ALBERT R. MANN LIBRARY
New York STATE COLLEGES OF AGRICULTURE AND HOME ECONOMICS
AT
CORNELL UNIVERSITY
Cornell University Library QK 94.L54 1868a
ai
Cornell University
The original of this book is in the Cornell University Library.
There are no known copyright restrictions in the United States on the use of the text.
http://www.archive.org/details/cu31924001400484
DESCRIPTIVE AND ANALYTICAL
BOTANY.
LONDON: PRINTED BY SPOTTISWOODE AND CO., NEW-STREET SQUARE AND PARLIAMENT STREET
A GENERAL
SYSTEM or BOTANY
DESCRIPTIVE and ANALYTICAL,
IN TWO PARTS.
PART I.—OUTLINES OF ORGANOGRAPHY, ANATOMY, AND PHYSIOLOGY.
PART IL—DESCRIPTIONS AND ILLUSTRATIONS OF THE ORDERS.
BY iO” ae geen Euu, LE MAOUT, J. DECAISNE, ( el a . DOCTOR OF MEDICINE ; MEMBER OF THE INSTITUTE OF FRANCE;
MEMBER OF THE SsOCIETE PHILOMATHIQUE OF PARIS. PROFESSOR OF CULTIVATION, JARDIN DES PLANTES, PARIS.
le
WITH 5500 FIGURES BY L° STEINHEIL AND A, RIOCREUX.
TRANSLATED FROM THE ORIGINAL BY
MRS. HOOKER.
THE ORDERS ARRANGED AFTER THE’ METHOD FOLLOWED IN THE UNIVERSITIES AND SCHOOLS OF GREAT BRITAIN, ITS COLONIES, AMERICA, AND INDIA; WITH ADDITIONS, AN APPENDIX ON THE NATURAL METHOD, AND A SYNOPSIS OF THE ORDERS, BY
a“ Loire
én J) D, HOOKER, CB, FRS. LS. & GS, M.D. D.C.L. Oxon, LL.D. Canrtas.
DIRECTOR OF THE ROYAL BOTANICAL GARDENS, KEW ; CORRESPONDENT OF THE INSTITUTE OF FRANCE.
LONDON : LONGMANS, GREEN, AND CQO. 1873.
All rights reserved,
poUeee
Univer 7 SITY|
Le iARY J
TO THE MEMORY OF
THE JUSSIEUS,
or ous 2 je . ‘AND TO
THE DISTINGUISHED EXPOUNDER OF THEIR DOCTRINES,
M. ADOLPHE BRONGNIART,
MEMBER OF THE INSTITUTR OF FRANCE : PROFESSOR OF BOTANY AT THE JARDIN DES PLANTES.
EDITOR’S PREFACE.
—c0p0300——
Tuts English reproduction of Le Maour and Decatsne’s work differs from the original published in Paris in 1868, first and mainly in the Natural Orders of Flowering Plants being arranged more nearly in the sequence followed in England and its dependencies, in the United States, and over the greater part of the Continent :—a course necessary to adapt it to the use of schools, universities, and the keepers of herbariums, botanical museums and gardens, in all English-speaking countries. This sequence, which is that originally proposed by De Candolle, and adopted with modifications by himself and by most classifiers, is further, in the opinion of the Editor, on the whole, the best linear arrangement hitherto devised.
The sequence of the Orders followed in the original is that of the late accomplished Professor Adrien de Jussieu, son, of Antoine-Laurent de Jussieu, the establisher of the Natural Orders of Plants upon the principles his uncle Bernard had devised. This sequence has been but partially adopted, even in Paris, where, although the lectures on the Natural Orders given at the Jardin des Plantes are conducted in accordance with it, the plants in the garden itself are arranged according to that of Professor
Adolphe Brongniart (see p. 165).
To render this part of the work complete, and to facilitate its use, I have added in an Appendix—what is a great desideratum in the original —a Conspectus of the Orders arranged under groups (cohorts), accord- ing to their affinities, in so far as this is practicable in a linear series. These groups are analogous to the ‘alliances’ devised by Lindley for his
viii EDITOR’S PREFACE.
‘ Vegetable Kingdom,’ though widely differing from them; they more nearly approach the ‘groups’ of Asa Gray’s ‘Introduction to Botany,’ and are identical with the ‘cohorts’ of Mr. Bentham’s and my ‘Genera Plantarum ’ in so far as these have been published, namely, to the end of Polypetale. The remaining Dicotyledonous Orders are grouped approximately by Mr. Bentham and myself, and are subject to rectification as we advance with our analyses of the genera for that work; for it must be borne in mind that no Natural Order or higher group can be accurately limited till all the genera belonging to itself and its allied groups have been thoroughly investigated, compared, and contrasted. For the grouping of the Monocotyledons I am alone responsible.
The next considerable deviation from the original consists in the intro- duction of various omitted Orders, and of much additional matter under the others, especially the tribes, sub-tribes, etc., of the large Orders, and in the increased numbers of genera (the selection of which is necessarily to some extent arbitrary) which “have been cited. This will render the English edition more useful to voyagers and travellers, and to dwellers in America, India and the Colonies, whose requirements in this respect have been especially regarded. ¥
The twenty-four Orders omitted in the original, and supplied here, are chiefly small ones ; but some, as XX., XXXIV., LVII., LXXIV., XCII., CLXVIIL., and CCXXI., are either of considerable extent, or of importance under other points of view. They are as follow :—
XX. CaNnELLACEA. CLXXXIX. Hernanviea. XXIV. VocHystacrai. CCIV. Prenamacea. XXXIV. DrIrPreRocarPEea. CCV. GEISsoLOMEs. XXXV. CHLENACES. CCVI. Lacistemacra. LVII. BursEraces. CCXYV. GRUBBIACEA. LIX. CHAILLETIACES. CCXXI. Poposrzmmacea. LXV. STackHOUSIEA. LXXII. Sasiaczea. MONOCOTYLEDONS. LXXIV. ConnaRaces. VII. Apostastacea XCII. RarzopHores. XVI. Trivxipea. CII. Samypacea. XLII. Roxsurcuracex CX. Fico1pra. XLV. Raparen.s,
CLXVII. Crescenviza. XLIX. Mayacea
EDITOR’S PREFACE. ix
. The number of Orders adopted in this work greatly exceeds that which
will be adopted by Mr. Bentham and myself in the ‘Genera Plantarum,’ or than is accepted by Professor Asa Gray, and most modern systematists : many of them are not in our opinion entitled to that rank, being rather to be regarded as tribes or aberrant genera of larger Orders. A multiplica- tion of these is, however, in a work of this description far from a great evil: it enables the student to form a clearer idea of the essential characters of the more important Orders, from which the lesser are departures; and it affords the opportunity of illustrating more copiously many structural and physiological matters of high importance. It will be observed that the authors have been scrupulously careful in indicating the very slender pre- tensions that many of these lesser groups have to ordinal rank, and in pointing out their affinities.
In dealing with the Introduction to Botany, p. 1, the Translator has had much difficulty. In point of style, a literal translation of the original was inadmissible ; its copiousness of expression and repetitions of adjective terms, however suited to French, are obstacles to English students, who associate clearness with a concise, rather than with a more diffuse method of exposition. The Translator has therefore condensed the matter of this part of the work—it is to be hoped, without loss of sense or substance ; and the space gained has been devoted to those additions to the Systematic portion which are enumerated above.
It will be obvious to the English reader, that it has not been the aim of the Authors to give an exhaustive history of the Natural Orders: what they have given is a clear and precise structural and morphological account of each, with a sketch of its affinities, geographical distribution, and principal uses in medicine and the arts ; and in this, I think, they have succeeded to a degree not attained in any previous work of the kind. On the extent and utility of the Illustrations there is no need to dwell; but it is only my duty to one of the Authors to state (which does not appear in the original) that their great value is due to the use made of my friend M. Decaisne’s unique collection of analytical drawings, the fruits of his life-long botanical labours, and which for scientific accuracy and artistic excellence have never been surpassed.
a
x EDITOR’S PREFACE.
Nearly thirty years have elapsed since I first had the privilege of inspecting those portfolios, the contents of which have, with a rare liberality, been ever since placed at my disposal when desired.
Few or no allusions are made under the Natural Orders to histological characters ; to the differentiation and development of the organs; to the phenomena of fertilization; to the functions of nutrition, circulation, and respiration; nor to the structural characters of Fossil Types, which, in the case of a few Orders (chiefly Cycadew and Lycopodiacew), are of great signi- ficance in reference to these and their allies. To have introduced all these subjects to any useful purpose was beyond the scope of this work. A companion.volume devoted to them—that is, one completing the Life-history of the Natural Orders—is the great desideratum of Botanical Science.
It remains for the Editor and Translator to thank the Authors for their confidence, both in entrusting them with the task, and in liberally per- mitting the re-arrangement of the Orders according to the Editor’s judgment of the requirements of those for whose use the English version is made.
Jos. D. Hooker. Royat Garpens, Kew: December 1872.
PREFACE.
—cobetoo——
Tue First Part of this work, together with the woodcuts illustrating the Natural Orders, is a reprint of the ‘ Atlas Elémentaire de la Botanique,’ edited by one of the Authors some years ago, and which has been favourably re- ceived by the scientific public. This, however, being devoted to European Orders, and confined to brief systematic descriptions only of these, could not illustrate the affinities of all the known types of the Vegetable Kingdom. To supply this deficiency, we have here added nearly all the exotic Orders, with detailed descriptions of their affinities and uses; so as to give such a general view of the Vegetable Kingdom as may be advantageously consulted by students and professed botanists.
For the sequence of the Orders we have followed the classification of A. de Jussieu’ in the valuable article on Taxonomy in the ‘ Dictionnaire Universel,’ simply inverting the series, so as to commence with the most highly organized, and end with the Families of lowest organization, whose history is still obscure.
The reader will observe that we have treated the Monocotyledons and Cryptogams with greater fulness than the Dicotyledons: this is because the two first, and especially the Cryptogams, having hitherto been much less fully studied than the Dicotyledons, required much more careful illustration.
We have also thought it best to detach from the larger groups many monotypic Orders, so as to give them greater prominence ; following in this
1 In this English edition the Editor has, with bodies of Great Britain, as well as of working bo- the approval of the authors, adopted that modifi- tanists, herbarium keepers, &c. A sketch of A. de cation of the elder Jussieu’s system known as De Jussieu’s sequence of the Families will be found in
Candolle’s, in order to suit the convenience of the the chapter devoted to Taxonomy (p. 167 ; see also Universities, Medical Schools, and other educational _p. 988).
xii PREFACE.
the example of our predecessors, who have appended the Genera affinia to the more strictly defined Orders.
Nearly all the illustrative analyses are original, and founded on materials accumulated during upwards of thirty years ; for all details taken from other sources the authority is cited.
Whilst thus presenting to our readers a comparative history of the Orders of Plants, we make no pretensions to having monographed them ; for such a task twenty volumes would not suffice, and its execution is already far advanced, thanks to the many first-class works which may be consulted by those who desire to investigate all the phenomena of the Vegetable King- dom. We have therefore restricted ourselves, in the departments of Anatomy and Physiology, to general considerations, and must refer our readers to the work of Duchartre for a detailed and lucid account of the present state of these two branches ; and to the ‘Genera Plantarum’ of Bentham and Hooker for all the elements of a complete treatise on Systematic Botany. On the subject of Geographical Distribution, the remarkable work of A. de Candolle contains an invaluable repertory of accurate data ; its value being enhanced by philosophical disquisitions of the highest order.
With regard to the series of portraits of Plants contained in this work, it is the richest and best arranged which has hitherto appeared; and we are confident that the public will appreciate, in these faithful drawings, the truthful pencils of Messrs. Steinheil and Riocreux.
ABBREVIATIONS. % Flowers with stamens and pistils (complete or hermaphrodite). ¢@ Flowers with stamens only (male or antheriferous). g Flowers with pistils only (female or pistilliferous). oo Indefinite in number. m. Magnified. * Before a genus, signifies that it is commonly to be found in French Botanic Gardens, &e. Note.—Sub placed before another word means nearly, somewhat, scarcely, &c.
The words rarely, sometimes, often, usually, &c., preceding a descriptive phrase, do not apply to varia tions occurring ih the same species, but signify that such variations occur in different genera of the Family under consideration,
The special terms used in the descriptions of Acotyledons are explained in the text as they occur.
COCLE
INTRODUCTORY CHAPTER.
PLANTS are organized living beings, void of feeling and voluntary motion; they constitute the Vegetable Kingdom; and Botany, which is the natural history of the Veyetuble Kingdom, treats of plants, firstly, individually ; secondly, collectively ; and thirdly, with regard to their uses to man. The whole subject may be con- sidered under three principal heads.
The first includes Organography, which treats of the form and symmetry of the organs of plants; Anatomy, of their interior structure; Physiology, of their func- tions; and Glossology, of the technical language employed to describe the organs and their modifications. .
The second includes Taxonomy, the classing of plants according to their affinities; Phytography, the description of species; and Nomenclature, the names given to species by botanists.
The third includes Agriculture, Horticulture, Arboriculture, Medical and Economic Botany.
The tissues of a plant present to the naked eye two very distinct elements, named fibro-vascular bundles and cellular tissue (parenchyma). The first consists of tenacious fibres gathered into bundles, or spread out like network, and forming the more solid portion of the plant; the second is a spongy, succulent substance filling the spaces between the fibres, being especially abundant in leaves and fleshy fruits, and constituting the softer portion of the plant. When magnified, these tissues present various structures, the components of which, called elementary organs, will be described in a future chapter.
An ordinary plant consists of a cylindric body (fig. 1), more or less branched at its two extremities, and bearing laterally leaves of various forms, which are either scattered or grouped. The upper portion of this body, the stem (caulis, T), bears the leaves (F,F), and is green (at least in the young shoots); it branches from the ground upwards, diminishing in thickness as it branches. The lower portion, the root (radia, R), is ‘leafless 1. Stock, Root and lower and subterranean, of a pale colour, and branches from above F downwards, diminishing in thickness the deeper it penetrates the earth.
Thus the stem and root are pnited where their girth is greatest, and are deve- loped in opposite directions; the former always tends to ascend, and the lower to C B
[
2 INTRODUCTORY CHAPTER.
descend, and they together constitute the vegetable axis. In its early stage this axis is simple, but by successive growths it usually gives off branches, which form secondary axes; each branch may thus be regarded as an independent axis.
The point of junction of the stem and root is the neck (collwm, c). It is from this point, which may be thickened, shortened, or obscure, that the ascending fibres of the stem and the descending fibres of the root diverge.
The stem, which alone possesses the power of emitting lateral expansions, develops from its sides more or less flattened bodies, the leaves (F). The point at which the leaves issue from the stem is generally thickened, and is termed a node (nodus); the intervals between the nodes are termed internodes (internodium, merithallus). When the nodes develop leaves only, the stem remains perfectly simple or unbranched ; but at each node a bud (gemnia, B, B) may spring from the axil of the leaf; and this bud, which appears at first as a small protuberance, afterwards becomes a branch (ramus), which lengthens, develops leaves, and ramifies in its turn. The buds springing from the axils of the leaves on the primitive axis thus give origin to as many fresh axes, whence it results that the mother-plant is repeated by every bud which it produces. Hence it is more logical to say that a plant multiplies, than that it divides by branching; and a vegetable may thus be looked upon, not as an individual, but as a collective being, or an aggregation of individuals nourished in common, like the zoophytes of a coral.
The node does not always produce a leaf and bud; the bud may be absent or scarcely visible, or the leaf may be imperfectly developed: but the latter is rarely entirely suppressed; and when the bud is undeveloped, it is owing to the rigour of the climate or the short duration of the plant.
Leaves are not developed promiscuously on the stem; they may be given off singly, when they are alternate (alterna, fig. 2); or two may be placed opposite to each other (opposita, fig. 3); or they may be whorled around the stem (verticillata,
3. St. John's Wort, 2. Toad-flax. Alternate leaves, Opposite leaves,
4, Madder. Whorled leaves,
fig. 4). Stem-leaves are rarely whorled, but floral leaves are arranged in several superimposed whorls (verticillt).
Alternate leaves, though apparently scattered without order on the axis, are really arranged in a spiral (fig. 5); so that, in starting from any one leaf (1)
we arrive, after one or more turns of the spiral, at another leaf ‘(6)
» placed
INTRODUCTORY CHAPTER. 3
directly above the first; whence it results that, if the leaves completing the Spiral (1, 2, 3, 4, 5) wee all placed on a level with the first, they would form a whorl around the stem. This arrangement is more easily traced on young branches of trees than on herbaceous stems.
The fibro-vascular bundle connecting the green expansion of the leaf with the stem is the petiole (petiolus, fig. 6). It extends from the axis to the blade or limb
5. Oak, Branch. 6. Cherry. Leaf. 7, Wallflower. Flower.
(limbus, lamina), which is composed of parenchyma and fibro-vascular bundles, which latter form the nerves (nervi, 1, 2, 8). The middle nerve of the limb, which is continuous with the petiole, is the median nerve or midrib (n. medius, costa media). The bundles which rise from each side of the midrib are the lateral nerves (n. late- rales); and these again give rise to secondary (2), tertiary (3), &c. nerves, according to their subdivision.
A leaf springing directly from the stem without a petiole is sessile (f. sessile, figs. 2-4), and that with a petiole is peteolate (f. petiolatum, figs. 5, 6). The leaf- blade is protected on both surfaces by a thin, colourless, and transparent skin (epidermis), which covers almost the entire plant, and will be described later.
The coloured leaves, arranged in whorls at the extremities of the ultimate branches of the axis, together form the flower (flos, fig. 7). The branch which immediately bears a flower, and forms the axis of its component whorls, is its peduncle or pedicel (pedunculus, pedicellus, fig. 7, Ped). Its more or less swollen extremity, upon which the whorls of the flower are grouped, is the receptacle (receptaculum, fig. 10, B).
In the most fully developed plants the flower is usually composed of four successive whorls (fig. 7), of which the internodes are suppressed. The outer or lower whorl is the calyx (calyx, figs. 7, s, and 8), the leaves of which are sepals (sepala, fig. 8). The whorl within or above the calyx is the corolla (corolla, fig. 7, P), and its leaves. are -petals (petala, fig. 9). When a petal is not sessile, but has its blade (L) borne on a petiole (0), this petiole is called the claw (wnguis).
B2
4 INTRODUCTORY CHAPTER.
The whorl within or above the corolla is the andrecium (andrecium, figs. 7, B, and 10), and its leaves are stamens (stamina, figs. 10, 8, and 11). The petiole of the stamen is the filament (flamentum), and its blade is the anther (anthera). The dusty parenchyma contained in the anther is called pollen (pollen, p). This pollen leaves the anther at a certain period,
8. Wallflower. 9, Wallflower. and, falling on the central Calyx (mag.). Petal.
5 Pa Wallflower. 11. Wallflower. organ of the flower, ASSIStS Anarecium and pistil (mag.), Stamen (imag.), in the formation of the seed. :
There frequently occur on the receptacle (fig. 10, R) small bodies (¢L) which secrete a sweet juice, named nectariferous glands or nectaries (glandule nectarifere, nectariu).
The whorl within or above the andrecium is the pistil (pistillum, fig. 12). This,
K® ea a] iS,
DAMA
, 15. Apricot. Pistil cut vertically (mag.), showing
12. Columbine.
Pistil composed of 5 carpels, 13. Columbine. the suspended ovule D, V, stigma s, with thescars of the stamens Ripe carpel pariially and axis of style'r, traversed by the on the receptacle rR. opened at the top, 14. Pea. Ripe pistil open. pollen to fertilize the ovule,
the central or last of the floral whorls, is composed of one or more leaves called carpels (carpidia, carpella, fig. 13), bearing on their edges small bodies called ovules (ovula), destined to reproduce the plant when fertilized by the pollen. The blade of the carpel, which encloses and protects the ovules, is the ovary (ovarium, fig. 12, 0); its prolongation upwards into a longer or shorter neck is the style (stylus, v) ; and the stigma (stigma, s) is an organ of variable form, spongy and viscous when young, usually placed on the top of the style, and destined to receive the pollen, which adheres to its surface.
The substance of an ordinary leaf, however thin, consists of three parts : (1) an upper and (2) an under surface, enclosing (3) a network of fibres and paren- chyma; and a slight inspection will show that a carpellary leaf is constructed on the same plan. Thus in the Pea, the pistil of which is composed of a single carpel, which splits into halves when ripe (fig. 14), the outer portion of the leaf {E) isa thin skin, easily torn away, named epicarp (epicarpiwm). The inner portion (rn)
INTRODUCTORY CHAPTER. 5
consists of a thicker and paler membrane than the first, named endocarp (endocar- pium). The intermediate portion consists of a more or less succulent tissue (accord- ing to the proportions of fibre and parenchyma), named mesocarp (mesocarpium). In the solitary carpel which forms the pistil of a Cherry (fig. 16), Peach, or Apricot (fig. 15), the epicarp (F) is a thin skin, the mesocarp (figs. 16, mE, and 15, £) is very thick and succulent when ripe, and the very hard endocarp (figs. 16, x, and 15, p) forms the stone.
The fibro-vascular bundles (fig. 14, L) which are found on the edges of the blade of the carpellary leaf, and which both bear the ovules (0) and transmit nourishment to them, are called the placente (plucente, trophospermia). Hach placenta produces lateral branches or cords, called funicles (funicult, Fr), which are sometimes very short, and through which the nourishing juices are conveyed to the seeds. When the funicles are absent (fig. 13), nourishment is transmitted directly to the seed from the placenta.
The seed or plant-egg (semen, fig. 17) is the ovule fertilized by the pollen. It is composed, (1) of a very small body, destined to reproduce the plant, the embryo (or plantula); (2) of an envelope or integument surrounding and protecting the embryo. This integument (in the ovule) either originates from the top of the funicle (fig. 17, F), or directly from the placenta (fig. 13). It usually consists of two layers or coats, an external testa (fig. 17,1), and an internal endopleura (gz). The point of union of the seed and funicle, and at which its nourishment enters, is called the hilum or umbilicus (fig. 18, H), and is a part of the testa. The chalaza (fig. 17, H) marks the spot where the juices penetrate the internal coat and reach the
16. Cherry. Ev &
:o4 Ripe carpel, cut vertically, a ee ae showing the seed suspentied Cc H A F Pp 18, Pea. by a funicle c springing Part of the in- from the bottom of the 17. Pea. Seed deprived of half its tegument of the kernel. integument (mag.). seed (mag.). 19. Pea. Embryo spread open (mag.).
embryo, and is usually indicated on the outside by a projection or thickening or discoloration. When the hilum and chalaza are superimposed, the juices reach the embryo directly ; when they are at opposite ends, they are connected by a small cord, raphe (figs. 17, a, and 18, R), which runs between the two coats. The small opening through which the ovule is acted on by the pollen is the micropyle (figs. 17, and 18, ).
The embryo (figs. 17, 19) is a complete plant in miniature, composed of a stem, caulicle (tigellus, cauliculus, T),.a root, radicle (radicula, R), one or two leaves, coty- ledons (cotyledones, c), and a bud, plumule (gemmula, plumula, eG), usually occupying a small pit (F) sunk in the thickness of the cotyledons. The young plant, after having been nourished by the juices transmitted through the funicle, detaches
6 INTRODUCTORY CHAPTER.
itself from the latter with its integuments; and when placed under favourable circumstances, it sheds or leaves its coats, and becomes developed into a plant similar to its parent.
The caulicle (v) is a small cylindric or conical body, bearing the first leaves of the plant (fig. 19, c), which ascends to form the stem. The radicle (x), or organ destined to develop the roots, is at first merely a transparent point terminating the free end of the caulicle, and tending downwards; it usually corresponds in the seed to the position of the micropyle (figs. 17, 18). The cotyledons (figs. 17, and 19, c), which are the first leaves of the young plant, spring laterally from the caulicle, and protect the plumule, or first shoot of the future plant; they are usually thick and succulent, and nourish the young plant until it is able to support itself. Within the integuments of the seed there always exists, at an early period, a peculiar form of cellular tissue, the study of which is important, and to which we shall recur ; it is sometimes rapidly absorbed by the embryo, but at others it is retained in the seed until germination, in which case it is called albumen, and supplies the young plant with its first food.
Considering the embryo as the plant in its simplest form, let us follow the growth and lateral development of its primitive axis. The two first leaves (cotyledons) are attached to the small stem (caulicle), as may , be seen in the Pea (fig. 19), or, better, in a germinating Bean (fig. 20,0, c). The radicle, which terminates the free end of the caulicle (fig. 20, T), sends out many descending branches, and forms the root (R). Sometimes the coty- ledon is solitary, as in the Maize (fig. 21, c), when the rootlets usually spring from various points of the caulicle (¢), and branch very little. | At the point of union of the cotyledons or “4 cotyledon with the caulicle is the plumule (fig.
20, ¢,¢, and fig. 21, g). Hach cotyledon and 20. Germinstion of Kidney- each leaf of the plumule is produced from a !
node, but the internodes are scarcely visible, 7! Germination of Maize. Soon after germination, as the plant grows and the axis lengthens, the nodes, and consequently the leaves, become separated. Near the flower the internodes of the axis shorten, the leaves usually become smaller and changed in form and colour; finally, at the termination of the axis, the leaves (flower), instead of forming a spiral or being placed in pairs, are arranged in superimposed whorls of different structure, the leaves in each whorl usually alternating with those of the next within or above it; which results in the blades of the different leaves composing the flower being separated as far as is compatible with being crowded in a very small space.
The leaves of the three first floral whorls (sepals, petals, stamens) have no buds in their axils or on their edges; those of the pistil alone (carpels) produce and protect buds; each edge of the carpel (placenta) giving origin to cords, which
INTRODUCTORY CHAPTER. 7
convey nourishment to one or more seed-buds (ovules), which eventually become seeds, consisting of an embryo with its integuments, which is destined to produce a plant similar to its parent. Though so dissimilar, the ovule or seed-bud presents a remarkable analogy to an ordinary bud: both spring from a node, and are protected by a leaf; both are destined to reproduce the plant. They only differ in the conditions of their existence: the seed-bud needing for its development the fertilizing action of the pollen; the branch-bud needing ouly the nourishment contributed by the node. To this must be added, that the branch-bud multiplies the plant without separating from it; whilst the seed-bud is destined to leave its parent, and reproduce at a distance the plant which gave it birth.
In some cases the branch-bud may be separated from its parent, and made to germinate, which is due to the power which the stem possesses of emitting from its surface supplementary or adventitious roots (r. adventitie). Sometimes a young branch, with its buds, may be detached from the stem, and planted, when the buried portion speedily sends forth roots, and the new individual becomes an independent organism: this is called propagating by slips or cuttings (talea). Or the branch, still attached to the trunk, may be surrounded with damp mould, into which it emits roots, which soon become snfficiently strong to nourish the branch, and to permit of its removal from its parent stem: this is termed propagation by layers (malleoli). Or again, the branch, with its buds, may be separated from its parent, and so attached to another plant, whose sap resembles its own, as to bring into contact the parts in which the sap circulates ; the branch then grows as if on its parent: this is called propagation by grafts, and the plant on which the branch is grafted is called the stock. Lastly, the branch-bud may separate spontaneously from the parent like a seed-bud, and falling to the ground, may strike root and become a separate individual, as in the Tiger-lily (fig. 22, B): such branch-buds are called bulbils (bulbilht).
The power of producing (naturally or artificially) buds and adventitious roots is
not confined to the stem, the | branches of many plants having also this power. The physiolo- ¢ gist Duhamel, having planted a tree with its branches in the ground, saw the roots become covered with buds, while the buried branches produced roots.
22, Bulbiferous Lily. In some cases the divided root 28, Bryophyltum,
Portion of stem. ‘ Leaf giving off embryos at each crenature,
will reproduce the plant, as in
the Japan Quince, the Osage Orange (Maclura), and especially the Paulownia, the roots of which may be cut into small sections, each of which, if planted, will produce a perfect tree.
In some plants the leaf itself possesses this reproductive power, as in the Watercress, Cardamine pratensis, and Malawis, &c., amongst native plants; and amongst exotics, Bryophyllum calycinum (fig. 28), a succulent tropical plant, whose
8 INTRODUCTORY CHAPTER.
leaf produces buds furnished with root, stem, and leaves, at the extremities of its lateral nerves ; these buds, which spontaneously fall off, and root in the earth, may be likened to embryos that do not need to be fertilized before developing; and the leaf of Bryophyllum may be regarded as an open carpel, on which the seeds have been developed by nutritive action alone. This fecundity of Bryophyllum completes the analogy between the true bud and the fertilized embryo.
Amongst the examples of reproduction by leaves, the Begonias hold the first rank; for if a Begonia leaf be placed on damp soil, and incisions made across its nerves, roots and buds will spring from every incision, and as many fresh plants will be obtained as the leaf has received wounds. The same vitality is observable in some woody plants: thus, if a fresh-cut Orange leaf be placed under suitable conditions of heat and moisture, a small swelling will be formed on the broken petiole, from which will shortly spring roots and shoots, that will eventually form a tree, capable of growing, flowering, and fruiting, like an Orange-tree raised from seed. ;
In this brief summary we have only spoken of the structure of the higher plants, whose organs of fructification being obvious, and their seeds provided with mono- or di-cotyledonous embryos, are called cotyledonous or phoenogamous (p. cotyledonee v. phenerogame). Other plants, which have no obvious stamens or pistils, and sceds without embryos, are called eryptogamous or Acotyledonous (p. cryptogamec v. acoty- ledonee), and are of much simpler organization.
ORGANOGRAPHY AND GLOSSOLOGY.
THE ROOT.
The root (radix) is that part of the plant which tends towards the centre of the earth ; it is not coloured green, even when exposed to light, and rarely produces leaves or shoots. It serves to fix the plant in the earth, and to draw thence the nourishment necessary to its growth.
The root is absent in certain plants, which, from growing upon and drawing their nourishment from others, are called parasites (p. parasitiew). Such is the Mistleto, which fixes itself beneath the bark of certain trees by the dilated base of its stem.
The root may be simple, or irregularly branched. Its axis or branches termi- nate in delicate fibrils, which together are termed the root-fibres (fibrille) ; the
24, Carrot. 25, Meadow-grass. 26. Dropwort, 27, Dahlia. Tuberous root. 28, -Orchis. Tapering root. Fibrous root. Nodose root. Tibrous-tuberous root.
tips of these fibres, being soft, loose, and cellular, are named spongioles (spongiole). The individual fibrils die annually, like leaves, and fresh ones spring from the youngest parts of the root.
Roots with a single, descending, vertical stock, are called tap-roots (r. perpen- dicularis) ; their main trunk or tap may branch (Stock, fig. 1), or remain nearly simple (Carrot, fig. 24). Sometimes the original, usually simple, tap-root perishes soon after germination, and is replaced by a bundle of fibrils, which spring from
10 ORGANOGRAPHY AND GLOSSOLOGY.
the neck or crown of the root. A root is fibrous (r. fibrosa) when its fibrils form a bundle of fine, long, scarcely-branched threads (Meadow-grase, fig. 25) ; nodose (7. nodosa), when the fibres are swollen at intervals (Dropwort, fig. 26) ; tuberous (r. tuberosa), when the fibres are much swollen in the middle, thus becoming stores of nourishment destined to sustain the plant (Dahlia, fig. 27). The Orchis root (fig. 28) is both fibrous and tuberous, the ovoid or palmate tubers being reservoirs of nutritious matters, and the cylirdrie fibres being organs-of absorption. The fibres of young Crocus roots are similarly swollen.
We have said that the stem has the power of emitting adventitious roots ; these are sometimes artificially induced (as on slips or layers), sometimes spontaneously developed on the nodes of the stem: when these emerge at a considerable height, and descend to enter the earth, they are termed aérial roots (many tropical climbers and epiphytal orchids); when they spring from the lower branches of creeping plants, they are called accessory roots (Strawberry, Ground-tvy).
THE STEM.
The stem (caulis) is that portion of the vegetable axis which grows in an opposite - direction to the root. It branches by means of shoots, which originate in the
axils of the leaves. The stem exists in all phenogams, but is sometimes scarcely developed, when the
leaves and flowering branches appear to spring from the root, and the plant is termed stemless (p. acaulis), and its leaves radical (f.radicalia, Hya- cinth, Dandelion, fig. 29), The stem is perennial (ce. perennis) when it lives many years (Strawberry) ; annual (c. annwus), when it only lives one (Wheat) ; biennial (c. biennis), when it lives two years (Carrot) ; a biennial stem usually produces leaves only the first year, and in the second it flowers, fruits, and dies. The stem is herbaceous (c. herbaceus) when soft and easily broken; such are annual, biennial, and many perennial stems; it is woody (c. lignosus, fruticosus) when it forms a solid, more or less durable wood (Oak) ; it is suffruticose (c. suffruticosus) when the lower part is hard, and remains above ground for many years, while the branches and twigs die, and are annually renewed (Rue, Thyme, Sage, Bitter-sweet). The woody stem of trees is called a trunk,
29. Dandelion, with root.
THE STEM. 11
The stem is indefinite (c. indeterminatus) when the flowers are borne only on the secondary axes (those springing from the axils of the leaves), thus appearing to elongate indefinitely (Periwinkle, Pimpernel, fig. 30).
; | fP |
30. Pimpernel. Indefinite stem. 31. Columbine. Definite stem.
The stem is definite (c. determinatus) when each axis terminates in a flower, and cannot therefore be indefinitely prolonged (Campanula, fig. 159; Columbine, fig. 31); it is aérial when it grows entirely above ground (Stock, fig. 1).
The rhizome or rootstock (rhizoma) is a stem which extends obliquely or hori- zontally below or on the surface of the ground, the advancing portion emitting fibrous roots, leaves, and shoots, the posterior gradually dying. The rootstock is indefinite (rh. indeterminatum) when it grows by means of a terminal shoot, which lengthens indefinitely, and never itself flowers, but gives off lateral flowering shoots. Thus in the Primrose (fig. 32) the extremity of the rootstock bears a bundle of leaves, in the centre of which is the shoot by which it is indefinitely prolonged, whilst the flowering shoot is developed in the axil of one of the leaves (z). After flowering, the aérial portion of the leaves dies, but the subterranean portion survives, and from its axil spring accessory roots.
The rootstock is definite (rh. determinatum) when, after producing laterally one or more creeping branches, it rises above the earth, and terminates its existence by a flowering branch. In the Iris (fig. 83) and Arum (figs. 34, 35) the leaf-bases
¢
ORGANOGRAPHY AND G@LOSSOLOGY.
35. Arum. Definite rhizome, cut vertically, showing two buds, the youngest whole,
34, Arum. Definite rhizome,
THE STEM. 13
persist as dry scales on the fleshy mass of the rootstock, after the decay of the aérial portions. é
In Curex (fig. 86) each shoot remains under ground during the first year of its existence; it'rises in the spring of the second year, makes a tuft of leaves, and emits from the
axil of the lowest of
these a shoot, which \ f lengthens during its \ \ first year, as its pre- decessor did. In the autumn the two-year- old shoot loses its leaves, but the axis, sheltered by their \ persistent bases, \ lengthens, and sends {\ i , up flowers and leaves “Qui, ee ene in the spring of the rt (To. ee te third year, when it | \ dies. During the fol- lowing autumn the flowering stem fruits and dies, together with the old shoot that produced it, but the second year’s shoot, which has now produced a tuft of leaves, will in its turn flower in the following year. A shoot of Carex thus requires three years for its full development.
The stem is stoloni- ferous (c. stolonifer) when creeping shoots ( flagellum) spring from the axils of its lower leaves, develop ter- minal tufts of leaves, then rise, and produce root- fibres below the tufts (Creeping Buttercup; Straw- berry, fig. 37). The rosette (propagulum) is the tuft of leaves produced on the lateral shoots of succulent plants (Houseleek).
The stem may present both stolons and rootstock when some of the lower branches are underground, and others aérial and creeping (Clubmoss).
The bulb (bulbus, Lily, fig. 38) is a subterranean swollen stock, consisting, firstly, of a more or less convex fleshy disk (lecus, L), which below gives rise to the roots ; secondly, of fleshy, closely-appressed coats or scales (gr) borne on the disk; thirdly. -of a more or less central shoot (T), equally borne by the disk, protected by the coats, and formed of rudimentary leaves and flowers; fourthly, of one or mor. lateral shoots, called cloves (bulbult), destined to reproduce the plant.
eae.
36, Carex. Definite rhizome.
37, Strawberry, Creeping stem.
14 ORGANOGRAPHY AND GLOSSOLOGY.
A bulb is coated (b. tunicatus) when the outer leaves overlap each other 80 as completely to sheathe the base of the stem (Narcissus, fig. 39; Onion, fig. 40) it is scaly (b. syuamosus) when the leaves are narrow, almost flat, and imbricated in many
39. Narcissus. Coated bulb, 388. Lily. Scaly bulb, cut vertically. 1, disk ; ¢, stem ; 7, leaves. 41. Colchicum. Solid bulb.
rows (Lily, fig. 38); solid (b. solidus) when the leaf-bases are very close and confluent with the disk, so that the latter appears to form the entire stock (Colchicum, fig. 41). In the Crocus (fig. 42), the underground
stock is formed of two or three solid bulbs, \ superimposed like the beads of a chaplet.
The primitive bulb (1), which terminates in
a flower, pushes out a lateral shoot, which ; perpetuates the plant. After flowering, it swells considerably, to nourish the shoot which is to succeed it; this latter flowers in its turn the following year, and emits a shoot like its predecessor; to nourish this it wo 40. Onfon. Coated bulb. swells and forms a bulb (2) above the original * C°c* Ssperimposed bulbs. one, which then gradually decays. At the flowering of the third shoot (3) adven- titious roots grow from the base of the second bulb, which soon withers and dries like the first. At the side of the middle bulb a lateral bulbil often springs, which separates from the parent, and becomes a fresh plant.
In comparing rootstocks with bulbs, it is easy to perceive that they differ only by the greater or less length of the disk, and the more or less fleshy texture of their underground leaves. The rootstock may thus be regarded as a bulb with a horizontally lengthened disk, and the bulb as a short rootstock with fleshy leaves.
THE STEM. 15
The superimposed rootstock of the Croeus presents a transition from the bulb to the rootstock proper, for it may equally be regarded as a vertical rootstock or as a series of superimposed bulbs.
The roots of Orchis, which are both fibrous and tuberous, are classed with true bulbs, differing from ordinary bulbs only in the swelling of some of the root-fibres. The two tubers are ovoid (fig. 48) or palmate (fig. 44), and are unequal; one (11) is dark-coloured, wrinkled, flabby, and empty, and gives off the flowering stem; the
43, Orchis. Tuberous root. 44, Orchis maculata. Palmate tuberous root. 45. Orchis maculata, Palma.e ttberous root, cut vertically.
other (rT 2) is larger, whiter, and more succulent, often ending in well-developed fibres (F), aud bears a shoot (B 2), from the base of which grow fibrous roots. The two tubers (fig. 45) are united above by a very short neck (Pp 1). This neck connects the old tuber (7 1) with the new one (rv 2), and from it the latter descends, and a leafy shoot (B 2) ascends, which in the following year will bear a flowering stem; between this large shoot and _ Ky the old stem a vertical cut reveals ih a third tiny shoot (B 3), developed eM from the young tuber, and destined to succeed it in the third year. There are thus three generations in the rootstock of an Orchis, each of which requires two years for its perfect development, and dies at the end of the third, after having flowered ; and the same may be seen -in Carex, Crocus, and ordinary bulbs. The term tubers (tubera, tuber- cula) has been given to the dilated extremities of underground roots, 46. Potato, Subterranean branches bearing tubercles. usually containing starch. These swellings bear rudimentary leaves, in the axils of which are eyes or buds, which develop into stems (Jerusalem Artichoke ; Potato, fig. 46). The conversion of shoots into tubers can be encouraged by earthing
16 ORGANOGRAPHY AND GLOSSOLOGY.
up the lower portion of the stem; if the covering is slight, the tuber swells but little; if the light can penetrate to the stem, the tuber becomes green, and produces rosettes of leaves.
Props (fulera) are a kind of aérial roots which spring from the axils of leaves, or from various points of the stem in certain climbing plants (Ivy, fig. 47), which are attached by them to walls or trees; these organs are non-absorbent, but under suitable conditions they behave like ordinary roots, as is seen with ivy cultivated for edgings.
Suekers (haustoria) are small warts upon certain parasitic stems (Cuscuta, fig. 48), whence issue true supplementary roots, which attach themselves to the neighbouring plants, and draw nourishment from their juices.
The stem is cylindiic or terete (c. cylindricus, teres), when a transverse cut presents a circular outline (Cabbage) ;—- compressed (c. compressus), when an elliptic
47, Ivy. Stem with props. 48. Cuscuta. Stem with suckers (mag.), 49, Pink. Nodose stem.
one, as if squeezed from opposite sides (St. John’s Wort, Tutsan) ;—triangular or trigonous (c. triangularis, trigonus), when a cut shows three sides (Carex) ;—square (c. quadrangularis, tetragonus), when it shows four right angles (Lamium) ;— pentagonal (c. quinquangularis, pentagonus), when it shows tive faces and five angles (Bramble).
The stem is glabrous (c. glaber), when there are no hairs on it (Horse-tail) ;— smooth (levis), when, being glabrous, it presents no roughness, and its surface is quite even (Tulip) ;—scubrous (c. seaber, asper), when its surface presents little inequalities (Carrot) ;—striate (c. striatus), when it is marked with small raised longitudinal lines or stricw (Sorrel) ;—winged (c. alatus), when furnished with foliaceous expansions (Comfrey, fig. 66) ;—nodose (c. nodosus), when its nodes are tumid (Pink, fig. 49) ;-— pilose (c. pilosus), when it is furnished with long scattered hairs (Herb-Robert) ;—
THE STEM. 17
pubescent (c. pubescens), when it is covered with more or less appressed short hairs (Henbane) ;—woolly (c. lanatus), when the hairs are long, close, appressed, and curly (Thistle) ;—tomentose (c. tomentosus), when the hairs are short, soft, and matted (Mullein) ;—villous (c. villosus), when the hairs are long, soft, and close-set (Forget- me-not) ;—hirsute (c. hirsutus), when it bears straight, stiff hairs (Borage) ;—hispid (c. hispidus), when the hairs are straight, stiff and very long (Poppy). The ana- tomical structure of hairs will be described hereafter.
The stem is prickly (c. aculeatus), when the hairs which clothe it thicken, harden, and end in a sharp point; the prickles (aculet) always belong to the epidermis, and come away with it (Rose, fig. 50) ;—it is spinous (c. spinosus), when the woody tissue of the stem is elongated into a hard point. Sypines (spine) are usually partially developed or arrested branches (Blackthorn, fig. 51), which, under favourable circumstances, produce leaves and shoots.
The stem is erect (c. erectus), when,,.m Jor vertical (Stock, fig. 1) <—eoinbent or = prostrate (c. procumbens, prostratus), when, too weak to support itself, it trails
50. Rose. Stem with prickles, 51. Blackthorn. $2, Bindweed. Twining stem. . 53. Hop. Twinitig stent.
along the ground (Knot-grass) ;—spreading (c. patulus), when many branches start from the neck, and spread on all sides horizontally (Pimpernel) 3 ascending (c. ascendens), when, after being horizontal or oblique at its commencement, its tip becomes upright (Speedwell) ;—creeping (c. repens), when a prostrate stem gives off adventitious roots from the nodes (Strawberry, fig. 37) s—scandent (c. scandens), when it raises itself by aid of neighbouring bodies, and attaches itself to them, either by props (Ivy, fig. 47), suckers (Ouscuta, fig. 48), or tendrils (Vine, fig. 1305 Melon, fig. 61) ;—the climbing stem is termed twining (c. volubilis), when it coils spirally round other bodies, rising either from left to right (c. dextrorsum, volubilis, Bindweed, fig. 52), or from right to Bi (c. sinistrorsum volubilis, Hop, fig. 53) of r placed opposite its convexity. os ee of ae branches depends on that of the leaves from the axils of which they spring; and they are alternate (r. altermi, Rose), opposite (r. opposite,
Valerian), or whorled (r. verticillati, Pine). . c
18 ORGANOGRAPHY AND GLOSSOLOGY.
The stem bearing opposite branches is dichotomous (c. dichotomus, Lamb’s Lettuce) ; and trichotomous (c. trichotomus, Oleander), when it continually forks or trifurcates to the extremities of its branches.
THE LEAVES.
Leaves (folia) are usually flat, green, horizontal expansions, arising from the nodes, and are the result of the spreading out of a bundle of fibres, the interstices between which are filled with parenchyma. The point of the stem constituting the base of the leaf, and of which the latter is a con- tinuation, forms a small swelling (pulvinus, fig. 54, c), which, when the leaf has fallen, is clearly indicated by a Scar (F).
54. Glycine. Branch, showing the buds _ 55, Orange. C; 57, Ranunculus. 56, Acacia heterophylus. after the leaveshave fallen. Leaf with a winged petiole. Leaf with amplexicaul petiole. Phyllode.
The leaves and roots are the principal organs of nutrition, absorbing from the atmosphere gases and liquids suited for the nutrition of the vegetable: they also act as respirators, and as exhalers of useless matters; and it is in their tissues that the sap, absorbed by the root, and conducted upwards by the stem, parts with its surplus fluids, and acquires all its nutritious properties.
Of all plant-organs, the leaves are those which present the greatest variety, and which supply most specific characters.
When the vascular bundle which enters the leaf is prolonged for a certain length before branching to form the skeleton of the blade (limbus), it takes the name
-of petiole (petiolus), and the leaf is called petiolate (f. petiolatum, Cherry, fig. 6) ;-— when it expands immediately after leaving the node, the leaf is reduced to its blade, and is called sessile (f. sessile, St. John’s Wort). When the blade merely narrows so as to form an obscure petiole, it is called sub-petiolate (f. sub-petiolatum).
The petiole may be cylindric (p. cylindricus) ; longitudinally grooved or channelled
v
THE LEAVES. 19
(p. canaliculatus); flattened horizontally, or depressed (p. depressus) ;—flattened laterally or compressed (p. compressus); in this case it is usually flexible, and the pendulous blade trembles with every breath of wind (Aspen).
The petiole is usually of tolerably uniform diameter throughout its length (p. continuus, Ivy, fig. 47); but it may be much dilated in the middle, and thus resemble a blade separated from the true blade by a constriction, when it is winged (p. alatus, Orange, fig. 55, Pp; Acacia heterophylla, fig. 56). Lastly, a dilated petiole
am S 7 ~( IN
59, Clematis. Twining petiole.
58. Wheat. Sheathing leaf. may replace the true blade, when it is called a phyllode (phyllodium), as in most Australian Acacias. When the enlarged base of the petiole, and the node from which it issues, occupy a large portion of the circumference of the stem, the petiole is called amplexicaul (p. ampleaicaulis, Ranwnculus, fig. 57); if the entire petiole is enlarged, and sheathes the stem, the leaf is called sheathing (vaginans, Carex, Wheat, fig. 58).
. i direction of the petiole is usually straight, but in some plants it twines round neighbouring objects (Clematis, fig. 59).
Stipules.—A leaf is stipulate (f. stipulatum), when provided at its base with appendages more or less analogous to leaves, named stipules (stipule, Heartsease, fig. 60). These may be persistent (s. persistentes), when they persist as long as the leaf which they accompany (Heartsease, fig. 60) ; or caducous (s. caduce), when they fall before the leaf, or as soon as the shoot lengthens (Willow, Oak).
c2
20 ORGANOGRAPHY AND GLOSSOLOGY.
60. Heartsease. Leaf with lateral stipules.
63, Meadow-grass. Leaf with a ligule,
65. Erophila. Radichl leaves.
66, Comfrey. Decurrent leaf. 67, Honeysuckle, Connate leaves, 68, Bupleurum. Perfoliate leaf,
THE LEAVES. 21
Stipules are foliaceous (s. foliacew), when of the colour and texture of leaves (Heartsease, fig. 60) ;—scale-like (s. squamiformes), when thin like scales ;—mem- branous (s. membranacee), when thin, flexible, and almost transparent ;—scarious (s. seartose), when dry and coriaceous (Beech, Willow, Hornbeam) ;—spinous (s. spinose), when contracted and hardened into spines (Rubinia, fig. 114); cirrhose (s. cirrhiformes), when they lengthen into twining tendrils (Melon, fig. 61). (We retain the name of stipules for the tendrils of the Melon and other Cucurbitacee, in deference to the glossology adopted by botanists; but we shall return to this subject when discussing tendrils.
Stipules are éateral (s. laterales), when inserted left and right of the leaf (Hearts- ease, fig. 60; Robinia, fig. 114) ;—aaillary (s. awillares), when in the axil of the leaf; they are then usually consolidated into one. Such axillary stipules may cover only a part of the circumference of the stem (Drosera), or may completely surround it (Buckwheat, fig. 62), in which latter case it bears the name of ochrea.
The ligule of grasses (ligula, Meadow-grass, fig. 63) is simply an axillary stipule (Lig.), situated at the separation of the blade (1) from the sheathing petiole (a) ; it may be entire, emarginate, laciniate, pilose, &c.
Of the whorled leaves of Madder (fig. 4) and other Rubiacew, the two opposite ones are alone considered as true leaves, and bear each a bud in its axil; the others are regarded as stipules, sometimes multiplied, when there are more than four, or confluent, when fewer than four.
The Nerves of the leaf are said to be parallel (n. paralleli), when they run free and parallel to the edge of the leaf and to each other (Iris, figs. 33, 79) ;—branching or anastomosing (n. ramost, anastomosantes), when they subdivide and join each other (Cherry, fig. 6).
Branching nerves are pinnate (n. punnati), and the leaves penni-nerved (f. penni-nervia), when lateral nerves, like the plumes of a feather, spring from the midrib (Cherry, fig. 6) ;—palmate (n. pal- mati, palmatinervia), when several primary nerves diverge from the base of the blade like the fingers of a hand (Melon, fig. 64). The primary nerves only are palmate; the secondary, tertiary, &c., are always pinnately arranged.
As regards position, leaves are radical (f. radi- calia), when they spring from near the neck, and hence appear to rise from the root (Dandelion, fig. 29; Plantain, Erophila, fig. 65) ;—cauline (f. caulina), when they spring from the stem and branches (Rose, fig.\50). Leaves are clasping or amplexicaul (f..ampleaicaulia), when the base of 69, Yew. Distichous leaves. their petiole or blade surrounds the stem (Rutter- Wy;
cup, Henbane) ;—decurrent (f. decurrentia), when™ ,cexied
their blade is continued down the stem, forming a sort of foliaceous wing; Wgmen™
22 ORGANOGRAPHY AND. GLOSSOLOGY.
74, Small mallow. Orbicular leaf.
71. Ranunculus aquatilis. Dissimilar leaves.
73. Sedum, Cylindrical leaves.
a as
78. Privet, 75. Pear. Lanceolate leaf. Ovate leaf.
76. Easter daisy. Spathulate leaf,
80. Juniper. WNeedle-shaped leaves,
79, Iris. Ensiform leaves. 77. Chenopedium, Angular leaf.
THE LEAVES. 23
the stem is then winged (caulis alatus, Comfrey, fig. 66) ;—confluent or connate (f. con- nata), when the bases of two opposite leaves join around the stem (Honeysuckle, fig. 67, Chlora) ;—when the base of a single leaf spreads completely round the stem, the stem and leaves are perfoliate (c. f. perfoliatus, Bupleurwm, fig. 68). Leaves are alternate (f. alterna, Stock, fig. 1; Toad-flax, fig. 2; Oak, fig. 5) ;—opposite (f. opposita, St. John’s Wort, fig. 3);—whorled (f. verticillata, Oleander, fig. 82; Madder, fig. 4) ;— distichous (f. disticha), when they spring from alternate nodes placed on two lines to right and left (Yew, fig. 69) ;—-fascicled (f. fasciculata), when crowded into a bundle on very short branches (Weymouth Pine, fig. 70). In true Pines this bundle is persistent ; in larches the leaves become solitary and scattered, in consequence of the elongation of the axis. Imbricated leaves (f. imbricata) overlap like roof-tiles (Houseleek, Cypress, Thuja).
Colour of Leaves.—Leaves are green when of the usual colour ;— glaucous (f. glawea) when of a whitish dusty green or blue (Poppy, Cabbage) ;—spotted (f. maculata) when they have spots of a different colour from the ground (Arum) ;— variegated (f. variegata) when they are of many colours arranged without order (variegated Holly, tricolowred Amaranth) ;—hoary (f. incana), when they owe their colour to short and close hairs (Ten-week-stock).
Forms of Leaves.— Without being precisely alike, yet the leaves of any one plant are usually very similar; but in some species they are obviously dissimilar (Paper Mulberry, Calthrop, Water Crowfoot, fig. 71; Shepherd’s purse, fig. 72); the plant is then said to be heterophyllous (pl. heterophylla).
Leaves are plane (f. plana), when their blade is much flattened, as is usually the case (Lime, fig. 86) ;—cylindric or terete (f. teretia), when the blade is rounded throughout its length (Sedum, fig. 73) ;—orbicular (f. orbiculata), when the circum: ference of the blade is more or less circular (small Mallow, fig. 74) ;—ovate (f. ovata), when the blade resembles the longitudinal section of an egg, with the larger end at the base (Pear, fig. 75) ;—obovate (f. obovata), when ovate, with the smaller end at the base (Meadow-sweet, St. John’s Wort) ;—oblong (f. oblonga), when the width is about a third of the length (small Centawry) ;—elliptic (f. elliptica), when the two ends of the blade are rounded and equal, like an ellipse (St. John’s Wort, fig. 3) ;— spathulate (f. spathulata), when the blade is narrow at the base, and large and rounded at the end, like a spatula (Haster Daisy, fig. 76) ;—angular (f. angulata), when the circumference of the leaf presents three or more angles ;—deltoid (f. deltotdea), if it presents three nearly equal angles, like a delta, A (Chenopodium, fig. 77).
ss os are lanceolate (f. lanceolata), when the blade is largest in the middle, and diminishes insensibly towards the extremities (Privet, fig. 78) ;—linear (f. linearia), when the sides of the blade are nearly parallel, and the space between them narrow (Toad-flax, fig. 2);—ensiform (f. ensiformia), when of the shape of a sword; in this case, the two surfaces are in apposition and consolidated in the upper part (Iris, fig. 79) ;—subulate (f. subulata), when the cylindrical blade terminates somewhat like an awl (Ledum reflecwm) ;—needle-shaped (jf. acerosa), when the blade is hard, narrow, and pointed like a needle (Pine, fig. 70, Juniper, fig. 80) ;—
*
24 ORGANOGRAPHY AND GLOSSOLOGY.
apillary (f. capillacea), when slender and flexible like hairs (Water Crowfoot, fig. 71) ;—filiform (f. filiformia), when thin and slender like threads (Asparagus, fig. 81). The false leaves of Asparagus here alluded to, and which have been described as leaves by most botanists, ought to be considered as branches springing from the axils of small scarious scales, which are the true leaves.
see BR
81. Asparagus. $2. Oleander, Acute leaves. 83. Pellitory. 84. Mistleto. 85. Amaranth.. Filiform leaves, Acuminate leuf, Obtuse leaf. Emarginate leaf,
Leaves are acute (f. acuta) when they terminate in a sharp angle (Oleander, fig. 82) ;—acuminate (f. acuminata), when the tip narrows rapidly and lengthens into a point (Pellitory, fig. 83) ;—obtuse (f. obtusa), when the tip is rounded (Mistleto,
86. Lime. Cordate leaf, 87. Ground ivy, 88. Bindweed. 89. Sheep's sorrel Reniform leaf. Sagittate leaf. Hastate leaf,
fig. 84);—emarginate (f. emarginata), when it terminates in a shallow sinus (Amaranth, fig. 85).
Leaves are cordate (f. cordata), when the base forms two rounded lobes and the tip is pointed, somewhat like an ace of hearts (Lime, fig. 86) s—reniform (f. reniformia), when the base is cordate but the tip rounded, like a kidney (Ground ivy, fig. 87) ;—sagittate (f. sagittata), when the base is lengthened into two sharp lobes, which are oblique or parallel to the petiole, like an arrow (Bindweed, fig. 88) ;—
THE LEAVES. 25
hastate (f. hastata), when the two lobes are nearly perpendicular to the petiole, like a halbert (Sheep’s sorrel, fig. 89);—~peltate (f. peltatum), when the petiole is joined to the centre of the under surface of the blade (Nasturtium, fig. 90), in which case the primary nerves diverge symmetri- cally from the petiole, like the spokes of a wheel. A peltate leaf may be compared with the orbicular palmately-nerved leaves of Mallows, for if the two
90. Nasturtium. Peltate leaves. 91, Curled Mallow.
edges nearest the petiole of the leaf of the small Mallow (fig. 74) were joined, a peltate leaf would be the result.
Surface of Leaves.—Leaves are smooth (f. levia), when their surface presents neither hairs nor inequalities (Orange) ;—scabrid (f. seabra), when rough or harsh to the touch (Carex);—glabrous (f. glabra), when, whether smooth or not, they have no hairs (Tulip) ;—silky (f. sericea), when clothed with long, even, shining hairs (Silver- aveed) ;—pubescent or downy (f. pubescentia), when they are clothed with soft short hairs (Strawberry) ;—pilose (f. pilosa), when the hairs are long and scattered (Herb- Robert) ;—villous (f. villosa), when the hairs are rather long, soft, white, and close (Forget-me-not) ;—hirsute (f. hirsuta), when the hairs are long and numerous (Rose-campion) ;—hispid (f. hispida), when they are erect and stiff (Borage) ;—setose (f. setosa), when they are long, spreading, and bristly (Poppy) ;—tomentose (f. tomen- tosa), when they are rather short, soft, and matted (Quince) ;—woolly (f. lanata), when long, appressed, curly, but not matted (Corn-centaury) ;—velvety (f. velutina, holosericea), when the pubescence is short and soft to the touch (Foaglove) ;-—cobwebby (f. arachnoidea), when the hairs are long, very fine, and interlaced like a cobweb (Thistle, Cobwebby Houseleek).
Leaves are wrinkled or rugose (f. rugosa), when their surface presents in- equalities, due to there being more parenchyma than is enough to fill the spaces between the nerves (Sage) ;—bullate (f. bullata), when this excess of pareuchyina renders the inequalities more visible, and the whole blade is swollen between the nerves (Cabbage) ;—crisped (f. erispu), when the extra parenchyma only appears at the edge of the blade, which appears crimped (Curled Mallow, fig. 91) ;—waved (f. unduluta), when for the same reason the edges are in rounded folds (Tulip).
26 ORGANOGRAPHY AND GLOSSOLOGY.
Hairs and Spines on the Margins of Leaves.—The leaf is ciliate (f. ciliatum), when its margins bear long hairs like eyelashes (Swndew, fig. 92) ;—spinous (f. spinosum), when the nerves lengthen and harden into thorns (Holly, fig. 93; Barberry, fig. 94); in Berberis, the leaves which first appear after germination are provided
with parenchyma like ordinary leaves, and the base of their petiole is furnished with two little stipules; but on the subsequent branches the stipules harden, lengthen into spines, and the leaf itself is reduced to one
94, Barberry. Spiny leaves. 92. Sundew. Ciliate leaf. 98. Holly. Spiny leaf. 95. Gooseberry. Spines.
or three thickened and spinous nerves, from the axils of which short branches, bearing ordinary leaves, are developed. In the Gooseberry (fig. 95) the three or five spines (c) which spring below the leaves (f) may be con- sidered as a development of the pulvinus of the leaf.
Divisions of Leaves.—The leaf is entire (f. integrum) when its blade is quite undivided (Oleander, fig. 82) ;—cut when its cdge, instead of being a continuous line, presents a series of broken
i) y |
96. Chestnut. Dentate leaf. 97, Archangel. Serrated leaf. 98, Elm. Bidentate leaf, 99. Hawthorn Incised leaf.
lines, owing to the parenchyma not accompanying the nerves to their extremities (Chestnut, Oak, Hawthorn) ;—dentate or toothed ( f. dentatwm) when it has sharp teeth
THE LEAVES. 27°
with a rounded sinus; it is the slightest way in which a leaf can be cut (Chestnut, fig. 96) ;—crenate (f.crenatum) when it has rounded teeth and a sharp sinus (Ground iwy, fig.87) ;—-serrate (f. serratwm) when the sinus and teeth are sharp and turned towards the tip of the leaf, like the teeth of a saw (White Archangel, fig. 97) ;—doubly-dentate or -crenate or -serrate ( f. duplicato-dentatum, &c.) when the teeth or crenatures are themselves toothed or crenate (Hlm, fig. 98) ;—incised (f. inciswm) when the teeth are very unequal, and the sinus sharp and deep (Hawthorn, fig. 99);—sinwate (f. sinuatum), when the divisions (deeper than teeth) and the sinus are large and obtuse (Oak, fig. 100). The divisions of the leaf are called laciniew! (lacinie), when acute, and separated by an acute sinus, which reaches half-way to the middle of the blade. If the nerves are pinnate, tle lacinie are so also, and
100. Oak. Sinuate leaf. 102. Castor-oil. Palmatifid leaf. 101. Dandelion. 103. Poppy. Pinnatifid runginate leaf. Pinnatipartite leaf. r
the leaf is pinnatifid (f. pinnatifidum, Artichoke) ;—if palmate, so also are the lacinia, and the leaf is palmate (f. palmatifidwm, Castor-oil, fig. 102). A pinnatifid leaf of which the lacinie point downwards, is called runcinate (f. runcinatum, Dande- lion, fig. 101).
The divisions of the leaf are called partitions (partitiones), when the sinuses extend beyond the middle, and nearly reach the midrib_or the base of the blade; according to the nervation the leafis then pinnatipartite (f. pinnatipartitum, Poppy, fig. 103), or palmatipartite (f. palmatipartitum, Aconite, fig. 104). The divisions of the leaf are called segments (segmenta), when the sinuses extend to the midrib or to the base of the blade; then, according to the nervation, the leaf is pinnatisect (f. pinnatisectum, Watercress, fig. 105) or palmatisect (f. palmatisectum, Cing-foil, fig. 106 ;? Strawberry, fig. 107). The divisions are termed lobes (lobi) when the sinuses
1 There are no current exact equivalents for the about the middle of the lcaf, and segments to divisions substantive terms lacinia, partitions, segments, and lobes _ to or near the base.—En. of this work; though when rendered into adjectives we 2 The Strawberry and Cing-foil have undoubted usually apply lobes to divisions which descend to or compound leaves.—Ep.
28 ORGANOGRAPHY AND GLOSSOLOGY.
are as long as those of the lacinie or partitions or segments, and when the divisions, of idefinite depth, are rounded; according to the arrangement of its nerves the leaf is then said to be pinnately lubed (f. pinnatilobatum, Coronopus, fig. 108), or palmately lobed (f. palmatilobatum, Maple, fig. 109).
104. Aconite, Palmipartite leaf, 105. Watercress. Pinnatiseot leaf. 106. Cinq-foil. Palmatisect leaf.
The leaf is lyrate (f. lyratum), when, being pinnati -fid, -partite, -sect, or pinnately lobed, it. terminates in a rounded division, much larger than the others (Turnip, fig..110) ;—pedate (f. pedatum), when NY woh /2 its lobes, segments, partitions, or lacinie diverge ' | YA from the base; this occurs when three palmate
ge divisions spring from the petiole, their midrib ee remaining undivided, whilst the two lateral produce on each side one or two parallel divisions, which are perpendicular to that from which they spring (Hellebore, fig. 111).
The same leaf is often variously divided ; thus the segments of the lower pinnatisect leaves of Chelidonium (fig. 112) are lobed,
sinuate, crenulate, and dentate; the lower ‘leaves of Aconite (fig. 104) are palmi-partite, with bifid or trifid partitions, and incised and
Ny toothed lacinie; the lower leaves of Herb-
Robert (fig. 113) are palmatisect, with trifid 108. coronopns. 107. Strawberry. Palmativect leat. seoments and incised and toothed lacinis,; P™nleted let the lacinie being rounded and abruptly terminated by a small point, and said to be apiculate (1. apiculate). The Castor-oil (fig. 102), Poppy (fig. 108), Cing-foil (fig. 106), and Maple (fig. 109), have toothed divisions.
Compound Leaves—A leaf is simple (f. simplex), however deeply cut its divisions may be, when these cannot be separated from each other without tearing, as in most of the leaves mentioned above. It is compound (f. compositum), when its component divisions can be separated without tearing; and its divisions are named leaflets
‘THE LEAVES. 29
(foliola). The petiole of a compound leaf is the common petiole (p. communis), and that of each leaflet is a petrolule ( petiolulus).
109. Maple. Palmately-lobed leaf. 110. Turnip. Lyrate leaf. 112, Chelidonium. Pennilobed leaf.
A leaf is simply compound, when the leaflets, whether petiolulate or not, spring, directly from the common petiole; and, according to its nervation, the leaf is
111, Hellebore Pedate leaf. 113, Herb-Robert, Palmatisect leaf. 114. Robinia. Pinnate leaf.
pinnate (f. pinnatum, Robinia, fig. 114) or digitate (f. digaitatum, Horse-chestnut, fig. 115; Lupin, fig. 116). When there are but few leaflets, their insertion must
30 ORGANOGRAPHY AND GLOSSOLOGY.
= ; i e a " # gi } um ,
117. Melilotus. Pinnate leat. 118. Trefoil, Digitate leaf.
119. Gleditschia triacanthos. Bipinnate leaf.
| y
120. Actaa spicata, Tripinnate leat. ‘121, Actrea racomosa,* Triternate*leat.
THE LEAVES. 31
be carefully observed: thus the Melilot (fig. 117) has a pinnately tri-foliolate leaf, but the Trefoil (fig. 118) a digitately ternate! leaf, all the leaflets springing from the top of the petiole.
, The leaf is bipinnate (f. bipinnatum), when the secondary petioles, instead of each ending in a leaflet, form so many pinnate leaves (Gleditschia triacanthos, fig. 119) ; tripinnate (f. tripinnatum), when the secondary petioles bear as many bipinnate leaves: (Actwa spicata, fig. 120) ; tri-ternate, when the common petiole bears three secondary petioles, which each bear three tertiary petioles, each of which again bears as many digitately tri-foliolate leaves (Actea racemosa, fig. 121). A pinnate leaf with all its leaflets in lateral pairs is termed pari-pumnate (f. pari-pinnatum) ; when im addition it is terminated by a solitary leaflet, the leaf is impari-pinnate (f. impari-pinnatum, Robinia, fig. 114).
125. Orobus. Pinnate leaf with unequal leaflet
Interruptedly pinnate leaf. Pinnatisect leaf, changed into a very short filament.
122. Caucalis. Decompound leaf. 123. Potato. 124. Agrimony..
A leaf is laciniate or decompound (f. laciniatuin, decompositum), when, without being really compound, it is cut into an indefinite number of unequal lacinix (Caucalis Anthriscus, fig. 122; Wuter Crowfoot, fig. 71), as in most umbelliferous plants (Parsley, Chervil, Hemlock, Carrot, Angelica, &c.). 7
A leaf is interruptedly-pinnate or -pinnatisect (f. interrupti-pinnatum, -pinnati- sectum), when the leaflets or divisions are alternately large and small (Potato, fig. 123; Agrimony, fig. 124).
Tendrils.—endrils (cirri) are thread-like, more or less irregularly spiral organs, which usually coil round neighbouring bodies, and thus support the plant. The leaf is cirrhose (f. cirrosum), when one or more of its leaflets is reduced to its median nerve, and becomes a tendril. In the Butter Vetch (fig. 125), the tendril is simple and very short, because it is only the terminal leaflet which is thus transformed. In the Pea (fig. 126), and in Vetches (fig. 127), the three terminal leaflets are changed into tendrils. In another Vetch (Lathyrus Aphaca, fig. 128) all the leaflets. are suppressed, and the whole leaf is reduced to a filament without parenchyma (v); in
1 More correctly a digitately tri-foliate leaf—En.
.
382 ORGANOGRAPHY AND GLOSSOLOGY.
compensation, the stipules (s, s) are very much developed, and perform the office of leaves. In Smilax (fig. 129), the petiole bears two lateral tendrils below the single
128, Aphaca. Petiolar tendrils.
Vv seeeenmeceren. fy i. = Sa 'o iH es f aN i, » AS
126. Pea. Leaf with tendrils formed from leaflets. 130. Vine. Tendrils formed from peduncles,
cordate blade, which may be regarded as the lateral leaflets of a compound leaf, reduced to their median nerves. The lateral position of the solitary tendril in the Melon (fig. 61) and other Cucurbitacee, together with the fact that two tendrils occasionally occur, one on each side of the leaf, has led most botanists to regard it as a stipule, of which the corresponding one is suppressed ; but the occurrence of two tendrils is very rare, and these are
: 127, Vetch, never precisely on the same level. On the Pinnate leaf with foliolar ten- drils and winged petiole.
129, Smilax. ‘ S ° Stipulary tendrils. other hand, unlike a true stipule, the
tendril of Cucurbitacee is derived from a vascular bundle remote from that which produces the leaf, and is separated from the petiole of the latter by buds. Upon
INFLORESCENCE. 33
the whole, the simplest explanation of the tendril of the Melon is, that, unlike that of the Pea and other Leguminose, it represents a leaf, reduced to one or more of its nerves: thus, when simple, it represents the petiole and mid-rib; when branched, it represents the principal nerves of the leaf, which are themselves palmately divided. In the Vine (fig. 130) the tendril is leaf-opposed, and formed of a branching peduncle (v, v), of which the pedicels are suppressed, but which sometimes bears imperfect flowers.
INFLORESCENCE.
This term (inflorescentia) is used in two senses, signifying both the arrange- ment of the flowers upon a plant, and a collection of flowers not separated by leaves properly so called ; the latter being the more special meaning of the term.
The organs of inflorescence are, (1) the supports of the flowers, Ch peduncle, pedicel, receptacle; (2) the er bracts (bractee), or altered leaves, OK from the axils of which the floral axes spring, and which are altered in colour and form, as they ap- ' proach the flower ; these are some- times absent (Stock and other Crucifere).
The peduncle (pedunculus) is a branch directly terminated by a flower; and its extremity forms the receptacle (receptaculum). This namie is also given to a more or less branched flowering axis, differing in appearance from the rest of the stem, bearing bracts, and of which the ultimate divisions are called pedicels (pedicelli).
Bracts vary in shape; they are usually small (Currant, fig. 132), and may be thin, transparent, and membranous (br. membranacee); or thin, dry, stiff, coloured, and scarious (br. scariose, Geranium); or coloured, like petals (Bugloss); they are very large in the Lime (fig. 131), which is peculiar in having the peduncle adnate to the midrib of the bract, and, though really axillary to it, appearing to rise from its centre.
The primary axis of the inflorescence is the common peduncle, whence spring the secondary, tertiary, &c. axes, according to their order of development.
The inflorescence is awillary (inf. axillaris), when the primary axis, instead of terminating in a flower, is indefinitely elongated, and the flowers are borne upon secondary axes, springing from the axils of its leaves (Pimpernel, fig. 30); it is terminal (i.’ terminalis), when the primary and secondary axes both terminate in a flower (Poppy, Columbine, fig. 31).
123. Currant. Simple 181. Lime. Bract joined to the peduncle.
taceme,
D
34 ORGANOGRAPHY AND GLOSSOLOGY.
In every inflorescence the flowers are solitary (fl. solitarit), when each peduncle is undivided, and springs directly from the stem, and is isolated from the others by normal leaves (Pimpernel, fig. 30). Inflorescence, in its restricted sense, consists of a group of pedi- celled flowers, bracteate or not, all springing from a common peduncle which bears no true leaves.
Indefinite inflorescences are—the raceme, corymb, umbel, spike, and head.
1. The raceme (race- mus) is an. inflorescence of which the nearly equal secondary axes rise along the primary axis; it is simple, when the pedicels spring directly from the primary axis, andterminate in a flower (Lily, Lily of the Valley, Snapdragon ; Our- rant, fig. 182; Mignonette,
183, Mignonette. Simple panicle. and called a panicle ( pani- 134, Yucca Gloriosa. Branch of compound panicle.
cula), when the secondary axes branch once or oftener before flowering (Yucca
Gloriosa, fig. 184). A thyrsus (thyrsus) is a panicle of an ovoid shape, the central pedicels of which are longer than the outer ones. 5
135, Cerasus Mahaleb, 136. Cherry. Simple umbel, 187. Fennel. Indefinite corymb. Umbel and umbellulz without involucre.
2. The corymb (corymbus) resembles the raceme, but the lower pedicels are so much longer than the upper, that the flowers are nearly on a level (Cerasus Mahaleb,
INFLORESCENCE. 35
fig. 135). In the Stock and many allied plants, the inflorescence is at first a corymb, but changes to a raceme as the primary axis lengthens.
3. In the umbel (umbella) the secondary axes are equal in length, and starting from the same point, flower at the same height, diverging like the rays of a parasol; it is a raceme of which the primary axis is reduced almost to a point. The umbel is simple (sertulum), when the secondary axes flower (Cherry, fig. 136) ; it is com- pound, when these bear umbellately arranged tertiary axes, called partial umbels (wmbellule, Fennel, fig. 1387; Carrot, fig. 188; Fool’s 159) santhues.
188, Carrot. Umbels with involucre ; Umbel without mvolucre ; umbellule with involucels, Parsl ey fig 1 39) umbellule with involucels. 3 . .
The bracts, which in most racemes spring, like the pedicels, from different heights, in many umbelliferous plants rise on a level, like the secondary and tertiary axes, and form a whorl. The name involucre (involucrum) is given to
- the bracts at the base of the umbel
140. Plantain. 141, Vervain. 142. Wheat. Simple spike. Simple spike. Compound spike.
143, Oat. Panicle of spikelets.
(Carrot, fig. 138), and that of involucel or partial involucre (involucellum) to the ‘ D2
36 ORGANOGRAPHY AND GLOSSOLOGY.
bracts at the base of the partial umbel (Fool’s Parsley, fig. 139). Both involucre and involucel may be absent (Fennel, fie. 137).
4. In the spike (spica), the flowers are sessile or subsessile on the primary axis (Plantain, fig. 140; Vervain, fig. 141). In the compound spike (s. composita) the secondary axes each bear a small
144. Willow. Staminiferous catkin. 145. Willow. Pistilliferous catkin.
distichous spike (sptkelet, Wheat, fig. 142). In many grasses, the spikelets are borne on long branching pedicels, forming a panicle (Oat, fig. 143).
The catkin (amentum) is a spike, the flowers of which are incomplete (i.e. they want either stamens or pistil), and which is deciduous when mature (Mulberry ; Willow, figs, 144, 145; Oak, fig. 146),
The cone (strobilus) is a catkin with large thick scales, principally found on certain evergreen trees, 146. Oak.
149, Arum. Spadix exposed by
; D é Staminiferous catkin. thi 1 of hence named Conifers (Pine, fig. 147). The spike vol the spat
part of the spathe, of the Hop (fig. 148) is a cone with large membranous bracts.
$e The spadia (spadix) is a spike of incomplete flowers, which, when oN young, is enveloped in a large bract or spathe (spatha). The axis of the spadix sometimes flowers throughout _ its length, sometimes the upper portion is flowerless (Arum, fig. 149). The branched spadix of Palms is called a ‘régime’ (in French).
5. In the head (capi- em en ea tulum) the flowers are
; . : collected into a head or depressed spike, of which the primary axis is vertically contracted, thus gaining
in thickness what it has lost in length (Scabious, fig. 150; Trefoil, fig. 151), and the
INFLORESCENCE. 37
depressed axis is called the common receptacle (clinanthiwm). As in the umbel, the head is usually bracteate, each flower springing from the axil of a bract. There
150, Scabious. Gapitntum, 151, Trefoil, Capitulum. 152. Marigold. Capitulnm with involucre.
should hence be as many bracts as flowers, but, owing to the crowding of the flowers, some of the bracts are usually suppressed. The outer Pract, or those below the outer flower, form the involucre (in-
volucrum, periclinium, Marigold, fig. 152). The bracts of the centre flowers are usually reduced to scales, bristles,
153, Camomile. 154, Cornflower.
Paleate receptacle, cut Bristly receptacle, cut , vertically. vertically. 155. Onopordon. Alveolate receptacle, ciit vertically,
or hairs. The receptacle is paleate (r. paleatum), when covered with scale-like bracts separating the flowers (Camomile, fig. 153) ;—setose (r.setoswm), when these are bristly ; such are often cut into fine hairs (Cornflower, fig. 154) ;—- pitted (r. alveolatum), when the flowers are seated in depressions, separated by variously shaped membranes, which represent the bracts (Onopordon, fig. 155). When these inner bracts are absent the receptacle is described as naked (r. nudum, Dandelion, fig. 156). Sometimes the base of the head is naked, or only protected by some normal leaves (T'refoil, fig. 151), but each flower may still be accompanied by a bract.
The inflorescences of Dorstenia Contrayerva, and of the Fig (hypanthodium), are also heads. In Dorstenia (fig. 157) the receptacle is much depressed or slightly
38 ORGANOGRAPHY AND GLOSSOLOGY.
concave, bearing incomplete flowers inserted in pits with ragged edges; in the Fig (fig. 158) the inflorescence is similar, but the receptacle is still more concave, inso- much that the male flowers, which are at the top of the fig, answer in position to the lowest flowers of the primary axis, and the small scales (bracts) at the mouth represent an involuecrc, which in the normal state would gird the base of the common recepta- cle, as in an or- dinary head.
It is obvious that every indefi- nite inflorescence must be a modifi- cation of the ra- ceme; thus the
|
tf i 156, Dandelion. 158. Tig. corymb is a ra-
157, Dorstenia, Naked receptacle. Cut vertically. . ceme with unequal
secondary axes, reaching the same level; an umbel is a raceme whose primary axis is undeveloped; the spike is a raceme whose secondary axes are undeve- loped; the capitulum is a spike with the primary axis vertically thickened and dilated. 3
The difference between the raceme, corymb, umbel, spike, and head being simply | due to the amount of development of the primary and secondary axes, these terms _ cannot be precisely limited, and intermediateterms are therefore frequently resorted to; as spiked racemes and panicles, when the pedicels are very short; a globose spike approaches the head; and an ovoid or spiked head approaches the spike. Amongst Trefoils, capitulate, spiked, and umbelled flowers all occur.
In the raceme, panicle, corymb, and spike, the pedicels flower from below up- wards, i.e. the lowest flowers open first. In simple and compound umbels, the outer flowers open first; whence we may conclude that the umbel is a depressed raceme. In the head, as in the depressed spike, the flowers really open from below up- wards, but as the surface of the inflorescence in both these cases is nearly horizontal, they appear to open from the circumference to the centre, and are called centripetal, a term which is applied to every indefinite inflorescence, whether the flowers open from below upwards, or from without inwards.
Definite Inflorescences.—These are all included under the general term cyme (cyma), however much they may be branched ; they are, the definite- or cymose-raceme}; true corymb ; wmbellate-cyme ; spicate-cyme, scorpioid cyme ; and contracted cyme, which comprises the fascicle and the glomerule.
1. In the definite- or cymose-raceme (Campanula, fig. 159), the flowering pedicels are of nearly equal length, as in the raceme; from which it differs in the primary axis (A, A, A), terminating in a flower, which is necessarily the first to expand;
INFLORESCENCE. 39
whilst of the secondary axes (B, B, B), the lowest, being the oldest, flowers first; and the tertiaries (c, c, c), although often lower than the axis whence they spring, flower last. The result is, that of the expanded flowers some are above, some below the buds, according to the order of the succession of their axes. When examining such inflorescences, the student must look for the axis terminated by a Hower, for the lateral leaf or bract which it bears, and for the shoot or secondary axis which springs be- tween this axis and itself.
159. Campanula. Cyimose raceme. "160. Cerastium. 161. Hawthorn. Definite corymb. Dichotomous cyme.
The racemose cyme is called a panicle or thyrsus when much branched (Privet) ; but in reality the differenee between the definite raceme and panicle is not analogous to the difference between the indefinite raceme and panicle, for the indefinite raceme consists of a primary and many secondary axes; while the indefinite panicle consists of primary, secondary, tertiary, quaternary axes; just as is the case both in the definite raceme and definite*panicle; the only difference between these two, then, is in appearance.
The definite raceme becomes a dichotomous cyme, when the primary axis termi- nates in a flower between two opposite leaves or bracts, from the axils of which spring two secondary axes, each again terminated by a flower between twe bracts, from the axils of which spring two tertiary axes, and so on (Cerastium, fig. 160); this evo- lution of subordinate axes, each terminating between two oppesite axes, is continued till the last axis fails, from deficient nutrition, to repeat the process. When, instead of two opposite leaves or bracts, there are three in a whorl below each successive central flower, with again three in their axils, the cyme becomes trichotomous.
‘ 9, In the definite (or true) corymb, the different flowering axes, although of unequal length, attain pretty much the same level (Hawthorn, fig. 161).
In the definite raceme and the corymb, the central flowers are first developed ;
in other words, the flowers open from within outwards, or centrifugally.
40 ORGANOGRAPHY AND GLOSSOLOGY.
3. In the definite wumbel or wmbellate cyme the pedicels appear to start from the same point as in the indefinite umbel, but the central flowers open first, and the outer pedicels are evidently the youngest and shortest : 5 being a definite umbel, flowering centrifugally, it is truly a cyme (Chelidonium, fig. 162).
4. The definite spike or spicate-cyme (Sedum, fig. 163)
162. Chelidonium. : Definite umbel. 163. Sedum. Spicate cyme. 164, Myosotis. Scorpioid cyme.
is composed of a succession of independent axes, alternating to the right and left, each terminating in an apparently sessile flower.
5. The scorproid cyme (Myosotis, fig. 164) is a raceme which rolls up in a crozier shape, like the tail - of a scorpion; it is composed of a / succession of in- dependent axes, which do not al- ternate right and left, but form an interrupted line, which tends to turn back upon it- self; in this in- ‘ florescence, them bracts are usually suppressed (fig. 165). | 6. In the con- 166. Box. Glomerule. tracted cyme the 167, Lamium. Fascicles on an indefinite stem. flowers are crowded, owing to the extreme shortness of the axes; it is called fascicled, when the axes are somewhat lengthened, and are regularly distributed
INFLORESCENCE. 41
(Sweet William) ;—glomerate, when the axes are almost suppressed, and extremely irregular (Boz, fig. 166).
Mixed inflorescences are those in which the definite and indefinite both appear. In the Labiate (Lamium, fig. 167) the general inflorescence is indefinite, while
169. Groundsel. Capitula in a corymb,
172, Butcher’s Broom. 170, Heartsease, 171. Bindweed. One- and two-flowered cymes. Epiphyllous flowers. ‘Bingle-flowered cyme.
the separate heads are true axillary cymes or fascicles. In the Mallows the same arrangement occurs (fig. 168). In Composite (Groundsel, fig. 169) the general inflorescence is a definite corymb, and the separate portions are heads. The definite inflorescence is sometimes reduced to a single flower, and resembles the one-flowered pedicels of an indefinite inflorescence (Heartsease, fig. 170); but a little below the flower two small bracts (bracteoles) will be found, in the axils of which are two obvious or suppressed shoots, which sometimes flower (Bindweed, fig. 171). The two bracteoles of a one-flowered pedicel are therefore the evidences of a two- or three- flowered cyme, of which the primary axis only is developed.
The inflorescence of certain plants has been called epiphyllous, from the flowers
!
42 ORGANOGRAPHY AND GLOSSOLOGY.
appearing to spring from leaves or bracts. In the Lime (fig. 131), the peduncle i: joined to the bracts. In Xylophylla the floral branch, dilated and flattened like a leaf, bears flowers along its edges. In the Butcher’s Broom (fig. 172), as in Xylophylla, the peduncles, enlarged into green leaves, rise in the axils of small scale: which are the true leaves, and bear on their centre one or more shortly pedicellec flowers, forming a cyme. .
THE FLOWER,
The flower, in phenogamic plants, is a collection of several whorls (usually four), formed of variously modified leaves arranged one above another in ring: or stages, so close that their internodes are not distinguishable.
The leaves which form each floral whorl are not always precisely on the same level, but often form a close spiral, and consequently not a true whorl; the terr whorl is, however, always applied to the calyx, corolla, andreecium, and pistil.
The flower may be regarded as a true shoot, terminating the peduncle or pedicel, and therefore terminal as regards the branch from which it springs; limiting the growth of that branch. . Its terminal position may >. be theoretically explained by supposing that
, the floral whorls exhaust the supply of nutri- ment provided by the.axis, and with this the = vegetative force necessary to prolong it. In the normal condition of the flower, the re- productive and nutritive forces are in equili- brium; but there are cases in which this equilibrium is disturbed,and in which the axis eat a eee lenethens beyond the floral whorls, and re- pea ty auow oe produces the plant by branch-buds; in which ogteaig cases the seed-buds are usually suppressed: this is seen ir many plants, and especially in proliferous roses (fig. 173). ei Prout rope nie: of which the peduncle is prolonged into a supplementary
c, C, calyx transformed into leaves >
of Ge aie teve | Goleman ads axis, ending usually in an imperfect flower (fig. 174) oi cane bade memeentine spor, Sepals (s) and petals (p), in the middle of which are a few tive carpels. imperfect stamens and carpels-
The variously transformed leaves composing the floral whorls, though modified in tissue, colour, and texture, to form the calyx, corolla, andreecium, and pistil, sometimes reveal their origin by resuming the aspect of normal leaves. The term anomaly or monstrosity is given to casual departures from the norma’ structure occurring in animals and plants, which anomalies are most frequently induced. by cultivation.
The first whorl or calyx, being the exterior, and therefore the nearest to the leaves, resembles these most.
The second whorl or corolla is more altered ;. the tissue of its petals is more
THE FLOWER. 43
delicate, and their colour more brilliant, but their claw, limb, and nerves, and their usually flat shape, all reveal their foliar nature.
The third whorl, or andreciwm, bears much analogy to the second ; the relative position of the stamens and petals is always the same, and these sonieunies present an insensible transition from one to the other; asin semi-double flowers, where some of the stamens are changed into petals; in partially double flowers, where all the stamens are so changed; and in full double flowers, where the carpels also have become ao see Columbine, Rose). In Rosa centifolia (fig. ne) par- s ¢6ticularly, the successive steps \ by which a stamen becomes a i petal are obvious; sometimes
the anther enlarges, and one cell reddens (6); or both cells
175, Transformation of stamens in roses. lengthen (5) 3 or the connective reddens and dilates, and bears on one side a yellow scale, which recalls an anther-cell (4, 3); oftenest the stamen expands at once 17«,
*. Hooded Columbine, into a complete petal (2); sometimes (1) the proximity of the RNs ore ee ant
anthers transformed and calyx seems to influence this petal; a green midrib traverses its °°™mec™*? together coloured blade, and it becomes sepaline in the middle, petaline on the sides. In the double Columbine (fig. 176), the anther swells, and forms a hooded petal; and some- times, but more seldom, the filament dilates into a flat petal.
The fourth whorl or pistil is the central; its position and the pressure of the surrounding organs influence its form in many ways, and hence disguise its origin ; but when the carpellary leaves are free (Columbine, fig. 12), or solitary (Pea, fig. 14), their foliaceous nature is obvious, and especially in anomalous cases, as the following.
Anomalies.—In the Columbine (fig. 177) the five carpellary leaves (F.c) instead
p ; of being folded to form a protecting cavity for the Sty {f | aAa- St young seed, have been found to remain flat, and > | bear along their edges (or placentas) small leaf-buds (r.o); these buds, which nor- mally would have contained © \ \ anembryo, were mostly open ; Fo... | In G/ 0—-- Fo some few, though empty, <s : | were curved, and suggestive of their normal fuuction; fertili- ve zation had not taken place, “\ pend the unfertilized stigma was reduced to a small glan- 178. Double Cherry. dular head (St), terminating Ha : re camenaay eld the midrib of the carpellary ~”™ ™*Uerneveorsiile: leaf. In the double Cherry (fig. 178), the free edges of the two carpels (F.c) bear no buds, and their blade or ovary, which altogether resembles an ordinary leaf, folded along its midrib (n.m), is lengthened into a style-like-neck, terminated by a spongy tubercle representing the stigma.
177, Monstrous Columbine.
4A ORGANOGRAPHY AND GLOSSOLOGY.
The Alpine Strawberry (fig. 179) presents a curious metamorphosis of the floral whorls. The calyx (s) is normal, the five outer leaves are bifid, and accurately represent the stipules of the leaves. The petals (P) appear as green, strongly veined, nearly sessile leaves
‘ 183. Alpine Strawberry. 179, Alpine Strawberry, 180. Alpine Strawberry. 181. Alpine Strawberry. 182, Alpine Strawberry. Carpel without the Green petal (mag.), Green stamens, Carpel (mag.). ovary (mag.),
with five acute ciliate lobes (fig. 180). The twenty stamens (fig. 179, ©) are arranged in four whorls, and are also expanded into green petioled simple or three- lobed leaves (fig. 181); most of them bear on each side of the base of the blade a yellow boss (a, A), representing a suppressed anther. The carpels (fig. 179, c), which have also reverted to leaves, are arranged spirally on a receptacle, which becomes succulent as the green flower grows. The carpellary leaf (fig. 182 F.c), the integument of the seed (F.0), called the ovulary leaf, and the embryo are transformed through excessive development into overlapping leaves. Of these, the outer leaf, often bifid (F.c), represents the ovary; its base sheaths the inner leaf (fig. 183, F.0o), which should have formed the outer integument of the ovule. At the inner base of this ovulary leaf (183, F.o) is a pointed shoot (P); this is the embryo, of which a vertical section (fig. 184) shows rudimentary leaves or cotyledons (co) and a plumule (4).
In this curious flower, an excessive supply of nutrition has deranged the reproductive organs, and the whorls, which should have been modified in
184, Alpine Strawberry. 185, Rumex. 186, Lily.
187. Narcissus. Carpel Flower with a double Flower with a double Flower with a duublemmotaleti perianth,
cut vertically. calycoid perianth. petalvid perianth. furnished with a cup simulating a corolla,
subservience to the function of reproduction, have preserved their original form of green leaves. Such a metamorphosis of all the floral organs into ordinary leaves ig not uncommon throughout the Vegetable Kingdom; it is called chloranthy.
THE FLOWER. 45
An incomplete flower (fl. incompletus) is one in which calyx, or corolla, or andreecium, or pistil is absent. The single or double whorl which surrounds the andrecium and pistil (or essential organs of the flower) is called a perianth (perianthium, perigonium).
A dichlamydeous flower ( fl. dichlamydeus) is one with a double perianth, i.e. with two whorls, calyx, and corolla (Wallflower, fig. 7); which are similar in form or colour or not. When both whorls are green and calyx-like (Rumez, fig. 185), the perianth is called calycoid, calycine, or foliaceous (p. foliacewm), and when both are coloured or corolla-like (Lily, fig. 186), itis called petaloid (p. petaloideum). In Nar- cissus (fig. 187) there is a fringed cup within the petaloid perianth, which is greatly developed in the common species here figured, but is much less so in the Narcissus poeticus, and other species. In these latter it is cut into six lobes, alternating with those of the double perianth, whence some botanists have concluded that it represents two confluent whorls analogous to the outer ones. Others regard this cup of Narcissus as formed by lateral expansion of the confluent filaments. In Orchis (fig. 188) the petaloid
188. Orchis. 190. Aristolochia. Flower with a double 189. Chenopodium. 191, Ash. Monoperianthed 192, Carex. irregular petaloid “Monoperianthed flower. Naked flower. flower with irregular d flower. perianth. perianth.
perianth has six unequal, spreading lobes, of which the upper are erect and form the hood (galea); the lowest is dilated, variable in shape, and called the lip (labellum) ; itis sometimes produced into a sae, or spur (calcar). : A monochlamydeous perianth (p. simplex) is usually con-~_ sidered as a calyx, and the flower is said to be apetalous (fl. apetalus). It may be foliaceous (Chenopodium, fig. 189), or petaloid (Anemone, fig. 230), or irregular (Aristolochia, fig. 190). An achlamydeous flower (fl. achlamydeus) has neither calyx nor corolla; it may be protected by one or more bracts (Carew, figs. 192, 193), or altogether unprotected (fl. nudus, Ash, fig. 191). A hermaphrodite flower (fl. hermaphroditus, 3) possesses both andrecium and pistil (Wallflower, fig. 7) ;—the flower is male (fl. masculus, g) when it has andreecium without pistil (Carex, fig. 192) ;—female (fl. feemineus, ¢), when it has pistil without andreecium (Carew, fig. 193) ;-—and neuter or sterile (fl. sterilis, neuter), when it has neither andrcecium nor pistil (outer flowers of the Cornflower, fig. 194) ;—
193. Carex. @ flower.
46 ORGANOGRAPHY AND GLOSSOLOGY.
moneecious (fl. monoic’), when the male and female flowers are on the same plant (Carex, figs. 192, 198; Oak, fig. 146; Hazel-nut, fig. 195, 195 bis, 195 ter; Arum, figs. 196,
195 bis. Filbert. og flower.
201. Mercurialis. g flower.
194. Cornflower.
Neuter flower. 199. Willow.
¢g flower.
195 ter. Filbert, © flower.
197, Arum. ¢ flower.
196. Arum, Moneecious flowers. Spa- dix bearing below the pistilliferous flowers, |
above the staminiferous, 198. Arum, 195. Hazel nut. and terminated by a club- 200. Willow. 202. Mercurialis.
Q flower. Moneecious flowers. shaped prolongation. © flower. flower. g
197, 198) ;—dicecious (fl. dioiet), when on separate plants (Willow, figs. 199, 200 ; Dog’s Mercury, figs. 201, 202) ;—polygamous (fl. polygami), when hermaphrodite flowers occur amongst the male or female (Pellitory). The general term diclinous (diclinus) is applied to moneecious, dicecious, and polygamous flowers.
THE CALYX.
The calyx (calyx) is the whorl placed outside of the corolla and andrecium. It is usually simple (Wallflower), sometimes double (Magnolia, Trollius) ; its component leaves are termed sepals (sepala). It is poly- sepalous (c. polysepalus), when its sepals are wholly separate (Wallflower, fig. 8; Colum- bine, fig. 31); gamo- or mono-sepalous (c. gamo-
or mono-sepalus), when its sepals cohere more or legs.
& A monos i 7 ; 208. Pimpernel, 204. Exythreea, 205. Lychmig, ae caly ne artite (c. partitus), Tive-partite calyx Five-fid calyx. Pive-toothed When e sepa Ss sd i ey pals are united at the base only ;
and it may be bi- tri- multi-partite (Pimpernel, fig. 203) ;—it is bi- tri- multi-fid, when the sepals eohere about half-way up (Comfrey,
THE CALYX. 47
Hrythrea, fig. 204) ;—-it is bt- tri- multi-dentate or -toothed (c. dentatus), when the sepals are united nearly to the top (Lychnis, fig. 205).
In the monosepalous calyx, the connected portion of the sepals is the tube (tubus), the free portion the limb (limbus), and the point of union of these the throat (faux).
Sepals are sometimes prolonged into appendages at the base, as in Myosurus (fig. 206) and Heartsease (fig. 500), where the five sepals are attached to the receptacle by their
206. Myosurus. 207, Campanula, 208. Lamium. 209. Larkspur.
Flower ay aati Appendiculate calyx. Irregular calyx. Calyx Prolonged nee a hollow centres; in some Campanulas (fig. 207) the appendage is formed by the union of two lobes belonging to two contiguous sepals, between which it is placed.
The calyx is regular (c. reqularis, equalis), when its sepals, whether equal or unequal, form a symmetrical whorl (Wallflower, fig. 8; Pimpernel, fig. 208 ; Erythrea, fig. 204; Lychnis, fig. 205) ;—it is irregular (c. irregularis, inequalis), when the whorl is unsymmetrical (Lamium, fig. 208). In the Aconite the upper sepal forms a hood ; in Larkspur (fig. 209) it is prolonged into a hollow horn or spur. In the Tropeolum (fig. 210), the spur is. formed by the united and lengthened three upper sepals. In Pelargonium the upper sepal is produced downwards, and forms a tube adherent to the pedicel. In Scutellaria the five sepals form two lips; of which the upper
211, Scutellaria, Young calyx.
210, Tropeeolum. Flower with calyx 212. Scutellaria, 214. Henbane. 213. Winter Cherry. prolonged into a hollow horn or spur. Ripe calyx. Urceolate calyx. Vesicular calyx.
protuberant one (fig. 211), after flowering, forms a shield to the ovaries, arching over them so as completely to envelop them, and meet the lower lip (fig. 212).
The tube of the monosepalous calyx may be cylindric (cylindricus, Pink, fig. 226) ; —cup-shaped (cupuliformis, Orange) ;—club-shaped (clavata, claviformis, Silene, Armeria) ; —bladdery (vesiculosus), when swollen like a bladder (Winter Cherry, fig. 213) ;—tur- binate (turbinatus), when it resembles a top or pear (Black Alder) ;—bell-shaped
48 ORGANOGRAPHY AND GLOSSOLOGY.
(campanulatus, Kidney-bean) ;—urceolate (urceolatus), when it resembles a small pitcher (Henbane, fig. 214).
The calyx is connivent (s. conniventia), when the sepals bend towards each other (Ceanothus) ;—closed (s. clausas), when their edges touch without joining (Wallflower, fig. 8) ;—-erect (s.erectas), when the sepals are vertical (Rocket, fig.
216. Fedia. Fruit crowned by a calyx with toothed limb.
217. Madder. 218. Chrysan- 219. Helianthemum.
Pistil crowned themum. Flower — Fruit crowned : 220. Valerian. el by a calyx with without a by a paleated calyx Fruit crowned by a calyx with 215. Quince. Fruit cut vertically. obsolete limb, calyx. (mag.). feathery tuft (mag.).
250) ;-—patent (s. patentia), when they spread horizontally (Mustard) ;—reflexed (s. reflexus), when turned back so as to expose their inner surface (Bulbous Crowfoot). The calyx-limb may be petaloid (Iris) ;—foltaceous (Quince, fig. 215) ;—toothed (Fedia, fig. 216);—reduced to a small membranous crown (Field Camomile)—or ring (c. margo obsoletus, Madder, fig. 217) ;—or altogether suppressed (Chrysanthemum, fig. 218) ; in the latter case the calyx is said to be entire (c. integer), because its tube is considered to be confluent with the ovary, and undivided. SAR NR ini g eis The calyx-limb may be reduced to scales Or (squame or palew, Helianthemum, fig. 219); or to radiating bristles or hairs, called a pappus (pap- pus). Sucha pappus may be plumose ( p. plumosus) when each of its hairs is covered with long secondary hairs or barbs visible to the naked eye (Va- lerian, fig, 220; Salsify, fig. 221) ; —simple (p.simplex) when the hairs or bristles are smooth and silky (Dandelion, fig. 222).
222. Dandelion. 223, Scabious. 221, Salsify. The pappus, whether simple or Fruit crowned by Fruit open (mag.). Fruit crowned by a calyx ze “i ere a calyx with a limb in Calyx with a with a plumose, is sessile (p. sessilis), when a simple tuft. stipitate tuft. feathery tuft.
the hairs are inserted directly on the top of the ovary (Cornflower, Valerian, fig. 220); stipitate (p. stipitatus), when the calyx-tube is prolonged into a slender neck above the ovary (Dandelion, fig. 222; Salsify, fig. 221; Scabtous, fig. 223).
THE CALYX. 49
The calyx is deciduous (c. decidwus), when it falls with the corolla after flowering (Wallflower, fig. 8) ;—caducous or fugacious (c. caducus), when it falls as soon as
[
224, Poppy. 229. Scabious. 225, Mallow. 227, Mallow. 228. Strawberry. Young flower. Involucred fruit Persistent calyx. Calycule of Flower with a calycule Caducous calyx. (mag.). whorled bracts, of stipules.
the flower begins to expand (Poppy, fig. 224) ;—persistent (c. persistens), when it remains after flowering (Pimpernel, fig. 203) ;—marcescent (marcescens), when it withers and dries up, and remains attached to the fruit (Mallow) ;—accrescent (c. accrescens), when it continues to grow after flowering (Winter Cherry, fig. 213). ‘Calycules’ and Calyciform Involucres.—The calyx is sometimes accompanied by whorled or opposite bracts, simulating an accessory calyx; to these have been given
the name of calycule or outer calyx (calyculus). The Pink (fig. 226) has a ‘ calycule’ E a
50 ORGANOGRAPHY AND GLOSSOLOGY.
of four bracts in opposite pairs. The Mallow (figs. 225, 227) has, outside the five-fid— calyx, a calycule of three bracts, and the Marsh Mallow one of six to nine bracts. .
231 bis. Winter Hellebore. Calyciform involucre near the flower.
233, Filbert, Fruits with foliaceous cup,
The five green bodies beneath and adherent to the calyx of the Strawberry (fig. 228), and which alternate with the five sepals, are not a calycule of bracts but of pairs of stipules belonging to the sepals. The pitted cup with fringed margins which encloses each flower of the Scabious (figs. 228, 229) may be considered a calycule.
Calycules are true one-owered involucres, ana- logous to the many-flowered involucres of heads and umbels.
The following are also one-flowered involucres : the three foliaceous cut bracts of Anemone (fig. 230),
placed far below the
~~ calyx;—the three entire
fy) bracts of Hepatica (fig.
231), also placed just
— below the calyx ;—the many foliaceous bracts Z ' of the Winter Hellebore ———— re (fig. 281 bis), placed
231. Hepatica. 232. Oak, Calyciform involucre near the flower. Fruit with a scaly cup,
235. Eupborbia, Calyciform many-flowered cup.
234, Chestnut, Prickly inyolucre, containing three frnits,
THE COROLLA. 51
almost in contact with the calyx ;—the cup (cupula) of the acorn (fig. 232), which is composed of small imbricated scales ;—the foliaceous cup, with cut margins, of the Filbert (fig. 233). The prickly cup of the Chestnut (fig. 234), and the calyciform cup of Euphorbia (fig. 235), only differ from the preceding in being many- flowered.
THE COROLLA.
The corolla (corolla) is the whorl next within the calyx; it is usually simple (Rose), sometimes double, i.e. composed of several whorls (Magnolia, Nymphea) ; its leaves are petals (petala).
Petals are usually coloured, that is, not green like the (usually foliaceous) sepals; some plants, however (Buckthorn, Vine, Narcissus viridiflorus), have green petals, while others (Helleborus, Aconite, Larkspur, Columbine, Fennel) have coloured or petaloid sepals.
In the polypetalous corolla (c. polypetala, dialypetala) the petals are entirely separate from each other (Wallflower, Strawberry, Columbine) ;—in the monopetalous or gamopetalous corolla (c. mono- gamo-petala) the leaves cohere more or less, so as to form a corolla of a single piece.
The corolla is regular (c. reqularis), when its petals, whether free or united, are equal, and form a symmetrical whorl; irregular (c. irregularis), when the reverse. A corolla may be formed of unequal divisions, and yet be regular; this is when the petals are alternately large and small, the small being all alike and the large all alike ; or when its divisions are oblique, but all alike, the whole corolla being still symmetrical (Periwinkle, fig. 274).
Polypetalous Corollas.—The petals are clawed (p. ungwiculata), when the broad part, or limb (lamina, fig. 9, L), is narrowed at the base into a petiole called the claw
236. Pink. 237. Ranunculus. 238. Barberry. 239. Lychnis. 240. Lychnis. Petal. Petal. Petal. Petal. Flower.
(unguis, Wallflower, fig. 9; Pink, fig. 236); the petals of the Rose and Ranunculus (fig. 237) are shortly clawed ; those of the Philadelphus and Orange are sessile.
The claw of the petal is nectariferous (u. nectarifer), when it bears a honey- secreting gland (Ranunculus, fig. 237); this gland may be protected by a scale (fig. 237), or naked (Barberry, fig. 238) ; and the claw itself is naked (u. nudus), when it bears neither gland nor scale (Wallflower, fig. 9; Pink, fig. 236); the claw is winged (u. alatus), when it bears a longitudinal membrane on its inner surface (Rose Campion). Little pits (fornices) are often found at the point of junction of the claw
B2
52 ORGANOGRAPHY AND GLOSSOLOGY.
and limb, or forming small swellings inside the tube (Lychnis Chalcedonica) ; they also sometimes occur in monopetalous corollas. Small scales, placed within and on
244, Nigella, 244 bis. Winter Aconite. 243, Helleborus, Two-lipped petal. Two-lipped petal. Tubular petal. 241, 242, 246. Columbine. 245. Trollius. 247, Aconite. Mignonette. Inner and lateral petals. Petal in a hood or Petal with one lip Flower naked, without calyx ; cornucopia, (mag.). petals hooded, pedicelled (mag.).
the top of the claw, forming a sort of crown around the andreecium and pistil, are collectively called a corona (coronula, Lychnis dioica, figs. 239, 240; Mignonette, figs. 241, 242).
The limb of the petal may be entire (Wallflower, fig. 9), or toothed or fringed (Mignonette, figs. 241, 242).
Petals are generally flat (p. plana), like the leaves; but may be concave (p. con- cava, Barberry, fig. 238) ;-—tubular with entire margins (p. tubulosa, Helleborus fetidus, fig. 243) ;—bilabiate (p. bilabiata), or tubular with the mouth two-lipped (Nigella, fig. 244; Winter Aconite, fig. 244 bis) ;—labiate (p. labiata), when the tube terminates in a single lip (Trollius, fig. 245) ;—hooded (p. cuculliformia, Columbine, fig. 246; Aconite, fig, 247);—spurred ( p. calcariformia), i.e, forming a spur or horn (Heartsease, fig. 248 ;
248. Heartsease. 249. Larkspur. Flower cut vertically, showing Petal in a spur formed of 250. Rocket, i the horn of the lower petal, four united petals, Tower. | ve Mion. of
Larkspur, fig. 249). Hollow petals, of whatever form, usually enclose at the base a gland which is nectariferous when the flower expands, and the anthers open to shed their pollen.
The regular polypetalous corolla is cruciform (ec. cruciformis), when it consists of four petals placed crosswise (Rocket, fig. 250; Chelidoniwm, fig. 251) ;—rosaceous
THE COROLLA. 53
(c. rosacea), when of five spreading, shortly-clawed, or sessile petals (Rose, Strawberry, fig. 252) ;—caryophyllaceous (c. caryophyllea), when of five clawed petals (Lychnis, figs. 239, 240).
The irregular polypetalous corolla is papilionaceous (c. papilionacea, Oytisus, figs. 253, 254), when composed of five petals, of which the upper or standard
252. Strawberry. 253, Cytisus, 254. Cytisus, 255, Cytisus, 257. Cytisus. Flower. Flower in profile. Front view of flower. Standard, Petals forming the keel.
(vexillum, fig. 255) is placed next to the axis; and encloses the four others in bud; of these the two lateral wings (ale, fig. 256) cover the two lower, which are contiguous, and often adhere by their lower margins, and together form the keel (carina, fig. 257).
Other irregular corollas are called anomalous (c. anomala, Aconite, Pelargonium, Heartsease, fig. 170).
Monopetalous Corollas.—In these, the tube consists of the united portions of the petals, the limb is the upper or free portion, the throat (faux) is the top of the tube, and is usually reduced to a circular opening, but is sometimes lengthened or dilated (Comfrey, fig. 268). It must be borne in mind that the term, limb, as
259. Heliotrope. _ 260. Heliotrope. 261. Pulmonaria. 262. Lycopsis, 263, Myosotis. Flower with naked Corolla laid open Corolla laid open Flower with bent tube Flower with closed throat (mag.). (mag:). (mag.). and closed throat (mag.). throat (mag.).
applied to the corolla, has two meanings; being used both to designate the blade of the leaf or petal, and the free upper portion above the tube of a gamopetualous corolla.
The throat is appendiculate (f. ap-~ pendiculata) when furnished inside with, and often closed by, variously formed appendages, which often answer to ex- ternal pits ;—it is naked (f. nuda) when
264. Myosotis. 265. Bugloss. Flower these are absent (Heliotrope, figs. 259, Corolla laid open (mag.). with closed throat (mag.).
260) ;—it is furnished with, but not closed by, long pencils of hairs in Pulmonaria (fig. 261) ;—closed by six swellings, each tipped with a pencil of hairs, and answering
54 ORGANOGRAPHY AND GLOSSOLOGY.
to so many external pits, in Bugloss (figs. 265, 266) ;—closed by five swellings, answering to pits, in Myosotis (figs. 263, 264) and Lycopsis (fig. 262) ;—closed by
268. Comfrey. 269, Comfrey, 266. Bugloss. 267. Borage. Flower showing the Corolla laid open, show- Flower cut vertically. Flower. pits between the ing the five scales be- (mag.). sepals. tween the five stamens,
five scales, conniving, and forming a conical roof over the tube, and answering to five external pits, in Comfrey (figs. 268, 269) ;—furnished with five emarginate scales, in Borage (fig. 267); and bearing a crown of long, narrow, cut scales, in Oleander.
The monopetalous limb is bi- multi-partite, when the petals cohere at their bases only (Pimpernel, fig. 277; Borage, fig. 267) 5
270, Campanula. 271. Cerinthe. 272. Chrysanthemum. * 974, Periwinkle. 273. Bindweed. Flower. Tower. Flower with tubular corolla. Flower. Flower.
—bi- multi-fid, when they cohere about half-way up, and the sinuses, as well as the segments, are acute (Tobacco, Campanula, fig. 270) ;—bi- multi-lobate, when the segments are obtuse or rounded (Myosotis, figs. 263, 264; Heliotrope, figs. 259, 260; Bugloss, fig. 265; Comfrey, fig. 268) ;—toothed, when the segments are very short (Heath, fig. 276). The regular monopetalous corolla is tubular (c. tubulosa), when iii) the tube is long and the limb erect and continnous with it (Cerinthe, ‘ _ fig. 271). The central flowers, called florets ( flosculi), *\. of Chrysanthemum (fig. 272) and allied plants with in- yolucrate heads, have small tubular corollas. Such heads are called flosculose. They are infundibuliform (c. infundt- es arenes o76. Heath, buliformis), when the tube insensibly widens upwards MONE: _ Mowers Vike a funnel (Bindweed, fig. 273) ;—hypocrateriform (c. hy- pocrateri- ormis or -morpha), when the straight and long tube abruptly terminates in a flat spreading limb, like an antique patera (Lilac, Jessamine, Periwinkle, fig.
THE COROLLA. ; 55
274; Bugloss, fig. 265) ;—campanulate (c. campanulata), when bell-shaped (Campanula, fig. 275) ;—-urceolate (c. urceolata), when the tube is swollen in the middle, and the mouth contracted, like a small pitcher (Heath, fig. 276) ;
. ; 281. Rosemary. 279. Lamium. 280, Galeobdolon, 277. Pimpernel. 278, Lamium. Labiate corolla with upper Front view of Front view of Flower. ‘Flower in profile. lip upright. flower. flower.
—rotate (c. rotata), when the tube is suppressed, and the segments horizontal, and divergent like the spokes of a wheel (Pimpernel, fig. 277; Borage, fig. 267) ;— stellate (c. stellatu), when rotate, with the segments very acute (Galiwm).
The irregular monopetalous corolla is bilabiate (c. labiata, bilabiata), when the limb is cut into two principal superimposed divisions (lips), and the throat is open; the upper lip consisting of two petals, and the lower of three. The upper lip may be entire, by the confluence of the two petals (Lamium, figs. 278, 279; Galeobdolon, fig. 280); or slightly split (Sage, Rosemary, fig. 281); or so deeply divided (Ger- mander, figs. 282, 283) that the two petals stand widely apart, and are confluent with the lower lip rather than with one another. In this case the corolla appears to consist of one five-lobed lower lip. Lastly, the upper lip is sometimes wholly suppressed, or distinguishable from the tube only by a notch (Bugle, fig. 284). The mid-lobe of the lower lip may be entire (Rosemary, fig. 281) ;—bifid (Lamium, fig. 279; Bugle, fig. 284) ;—trifid (Galeobdolon, fig. 280).
The personate corolla (c. personata) is a form of the labiate, with the throat closed by a projection of the lower lip, called the palate (palatum) ; in many personate corollas the tube is tumid at the
’ 83. Germander. 284, Bugle. 285. Snapdragon, ieee anes awe in: Roa, Labiate corolla with upper lip almost obsolete. Tigwen base in the direction of the lower lip, and called gibbous (c. gibbosa, Snapdragon, fig. 285), or even spurred (c. calearata, Linaria, fig. 286).
Two-lipped corollas are often described as ringent (c. ringens), but this term being equally applied to both the labiate and personate corollas, it is superfluous.
56 ; ORGANOGRAPHY AND GLOSSOLOGY.
The ligulate corolla (c. ligulata) consists of five confluent petals, of which the two upper join at their base only, but unite almost throughout their length with the three others, as do these with each other, so that the corolla has a very short tube, and a limb en- tirely formed of a finely-toothed
287. Chrysanthemum, 288. Foxglove, 289. Cornflower. 291. Centranthus. 286. Linaria. Flower with Flower with Sterile floret Flower (mag.). Flower. ligulate corolla. anomalous corolla. (mag ).
ligule (Chrysanthemum, fig. 287). Ligulate flowers are usually collected in an in- volucrate head, and are called semi-jlorets (semi-flosculi). A head (capitulum) composed of semi-florets is called semi-flosculose (Dandelion); one with tubular florets in the centre, and ligulate ones in the cir- cumference, is rayed (c. radcatum, Chrysanthemum, Marigold).
All other irregular monopetalous corollas are considered to be anomalous (c. anomala). Of these the corolla of the Fow- glove (fig. 288) resembles a thimble; the flowers on the cir- cumference of the Cornflower (fig. 289) are large, irregular, and 290. Seabions. Ray floret. neuter; those of the Scabious (fig. 290) are also very irregular and almost labiate; and Centranthus (fig. 291) has an irregularly hypocrateriform corolla, with an inferior spur to the tube.
THE ANDRCCIUM.
The andreciwm (andrecium) is the simple or double whorl, placed within or above the corolla; the leaves composing it are called stamens (stamina). A complete stamen (fig. 292) consists of a petiole or filament ( jullamentum, F) and a limb or anther (anthera, a); the anther is halved vertically by a median nerve, the connective (connectivum, c); each half consists of a cell (loculus, L) formed of two valves, the junction of which is marked externally by a furrow or suture. The back of the anther faces the corolla, and its face is opposite the pistil. The cellular tissue of the anther-cells is originally soft, pulpy, and continuous ; but when the anther is mature, this tissue becomes dry and powdery; the two valves then separate along the suture; the cell opens, and the parenchyma cells,
THE ANDR@CIUM. 57
now called pollen, are ready to be conveyed to the stigma. The anther is tarely sessile, i.e. without filament (Arum, fig. 293).
When the corolla is monopetalous, the stamens almost invariably adhere to it
292. Stock, 294. Belladouna. 295. Campanula, 296, Ranunculus. Stamen, Corolla and andreecium laid open. Flower cut vertically. Pistil and stamens.
(Belladonna, fig. 294) ;—amongst the few exceptions are Heaths and Campanulas (fig. 295).
Insertion of the Stamens.—This term relates to the position on the floral axis which the stamens occupy relative to the other whorls. The insertion of the corolla always coinciding with that of the stamens, in the staminiferous monopetalous corolla the insertion of the stamens may be inferred from that of the corolla. Thus the stamens, like the corolla, are hypogynous (st. hypogyna), when they do not adhere to the pistil or calyx, but spring from the receptacle below the base of the pistil (Ranunculus, fig. 296 ; Primrose, fig. 297) ;—perrgynous (st. peri- gyna), when inserted on the calyx, rather above the base of the pistil, to which they are relatively lateral (Apricot, fig. 298;
Campanula, fig. 295) ;—epigynous (st. epigyna) when >, inserted on the pistil itself (Coriander, fig. 299 ; ‘\ Madder, fig. 300).
297. Primrose. 300, Madder. 298. Apricot, 299, Coriander. Flower cut vertically (mag.). Flower cut vertically. Open flower. Flower cut vertically.
The perigynous and epigynous insertions being easily confounded, the term calycifloral (pl. calyciflore) has been given to all plants whose corolla (whether mono- or poly-petalous) and stamens are inserted on the calyx, and this whether the calyx be below the ovary (Apricot, fig. 298), or above it (Campanula, fig. 295; Coriander, fig. 299; Madder, fig. 800). The term thalamifloral (pl. thalamiflore) has been given to plants whose polypetalous corolla and stamens are inserted below the pistil, or hypogynous ; and corollifloral to plants with a monopetalous staminiferous corolla ‘inserted below the pistil, or hypogynous (Primrose, fig. 297).
58 ORGANOGRAPHY AND GLOSSOLOGY.
Number of the Stamens.- The flower is isostemonous (jl. isostemoneus), when the stamens equal the free or united petals in number (Coriander, fig. 299; Primrose, fig. 297) ;—anisostemonous (fl. anisostemoneus), when they are fewer than the petals (Valerian, fig. 301; Centranthus, fig. 291; Snapdragon, fig. 305), or more numerous than the petals (Sedum, fig. 302; Horse-chestnut, fig. 303 ; Ranunculus, fig. 296) ;—
Y
diplostemonous ( fl. diplostemoneus), when more than double the petals (Ranwn- culus, fig. 296; Myrtle, fig. 304). The flower, according to the number of stamens, from one to ten, is said to be
301. Valerian. 302. Sedum, 303. Horse-chestnut. 304, Myrtle. Flower (mag.). Flower, Flower. Flowering branch.
mon-, di-, tri-, tetr-, pent-, hex-, hept-, oct-, enne-, dec-androus; when above ten, the stamens are called indefinite (st. plurima), and the flower polyandrous (fl. polyandrus). Proportions of the Stamens.—Stamens are not always equal: they are didynamous (st. didynama, Snapdragon, fig. 305), when four, of which two are the longest; this occurs in irregular monopetalous normally pentandrous flowers, in which four stamens alternate with four of the five lobes of the corolla, and the fifth stamen: is suppressed. Stamens are said to be tetradynamous (st. tetradynama) when six, of which two are small and opposite, and four large, and placed in opposite pairs (Wallflower, fig. 306) ; these pairs . being in juxtaposition, their fila- se ras ag Cee
305. Snapdragon. Andreecium and half 306. Wallflower. 307. Stellaria. of corolla. Andrecium. Androecium,
308. Meconopsis. ‘ Flower cut vertically.
ments sometimes cohere, so that each pair has been supposed to represent a double stamen. In polystemonous or diplostemonous flowers, the whorls of stamens
are often unequal (Stellaria, fig. 307), but there is no special term for this modifi- cation.
Cohesion of the Stamens.—Stamens are free (st. distincta, libera), when completely
THE ANDRGCIUM. 59
independent of each other (Meconopsis, fig. 308) ;—monadelphous (st. monadelpha), when the filaments are more or less united ina single tube (Ozalis, fig. 309; Mallow,
509, Oxalis. . 310. Mallow. 312. Lotus. Androecium and pistil. 313, St. John’s Wort. Andrceecium and pistil. Androecium (mag.). Flower cut vertically.
fig. 310; Cytisus, fig. 311) ;—diadelphous (st. diadelpha), when united into two columns (Lotus, fig. 812);—triadelphus (st. triadelpha), when in three bundles (St. John’s Wort, fig. 318) ;—polyadelphus (st. polyadelpha), when in several simple or branched bundles (Orange, fig. 314; Castor-oil, fig. 315) ;—syngenesious (st. syngenesa), when the anthers cohere (Thistle, fig. 316). Sometimes the co- hesion extends to the filaments also (Lobelia, Melon, fig. 817). The stamens are said to be gynandrous (st. gynandra),
816. Thistle. 314. Orarge. 318. Aristolochia. Andrecium Calyx and 315, Castor-oil. 317. Melon. Andreecinm
(mag.). andrecium. ¢& flower. Andrecium (mag.). . and pistil (mag.). when they are united throughout their length to the pistil (Orchis, fig. 188 ; Ari- stolochia, fig. 318) ; in this.case they are necessarily epigynous.
The filament may be . cylindric or filiform (Rose), or capillary (Wheat, fig. 835), or subulate or awl-shaped (Tulup, fig. 845), or flat and dilated at its base (Campanula, fig. 819). It is said to be bi- tri- cuspidate, when forked at
the top, or three-toothed, Ny
with the mid-tooth antheri- 319, Lee 320. Onion. ‘g rhe come ‘i. Price sais x Pistil and stamen. Stamen (mag.). ndreecium and pisti tamen (mag, ferous (Garlic-onion, fig. *’™enesame ‘
’ 320;. Orambe, fig. 321) ;—appendiculate, when it bears an appendage; such
60 ORGANOGRAPHY AND GLOSSOLOGY.
appendages are of various shapes and sizes, and may be produced before or behind * the anther. In Borage (fig. 322), the anther is horned; in Self-heal (fig. 328), it is forked, &c. In the Mountain Alyssum, the filaments of the long stamens bear a
\ 828, Alchemilla.
j Stamen (mag.).
823. Self-heal, 824, Alyssuth. 325. Alyssum, 826. Butomus. 327, Polygila. 329. Mallow. Stamen (mag.). Long stamens, Short stamen. Stamen (mag.). Andreecium (mag.). Stamen (mag.).
toothed wing on their inner face (fig. 324), and those of the short stamens have an oblong appendage at the base in front (fig. 325).
Anther.—-The anther is two-celled (a. bilocularis), when the two cells are sepa- rated by a connective (Wallflower, fig. 11) ; each cell being originally divided in two by a partition or plate springing from the connective, of which no trace remains at maturity ;—fowr-celled (a. quadrilocularis), when this partition remains (Butomus, fig. 326) ;~one-celled (a. unilocularis), when it presents only one cavity (Polygala, fig. 327; Alchemlla, fig. 328); this often happens, either by suppression of one cell (Mallow, fig. 329), when the filament is lateral; or by fission of the stamen (Horn- beam, fig. 330). Sometimes the anther is seated on a flat-lobed connective, when it contains as many cells as there are lobes of the connective (Yew, fig. 331).
The anther is adnate (a. adnata), when its cells are confluent with the con- nective throughout their length (Hepatica, fig. 8332). The connective is sometimes very short, connecting the anthers by a mere point. The anther is didymous (a. didyma), when the point of union of the cells is above their middle (Huphorbia, fig. 333) ;—two-horned (a. bicornis), when, the point of the union being at the base of the cells, the latter are
830. Hornbeam. 331. Yew, 332. Hepatica, 833. Enphorbia. 334. Heath. Stamen (mag.). Flower (mag.). Stamen (mag.), g Flower (mag.). Stamen (mag.).
335, Wheat, Spikelet (mag.).
erect and slightly diverge (Heath, fig. 334) ;—cruciate, when the point of union of the cells is precisely in the middle, and their extremities are free (Wheat, fig. 335) ;—
THE ANDR@CIUM. 61
sagittate (a. sagittata), when the upper portions only of the cells are united by the connective, and the lower portions slightly diverge (Wallflower, fig. 11; Oleander, fig. 340). The anther is usually ovoid, but »~<=
may be oblong, elliptic, globose, square, &e. 3 (2, it is acute in the Borage (fig. 322), and sinuous in the Melon (fig. 317).
The connective is sometimes developed
Stamen,
342, Pine. 344. Cypress. Stamen (mag.).
341. Heartsease. 336, Lime. 337. Periwinkle. 338. Sage. 339. Rosemary. Two stamens, one 340, Oleander. Stamen (mag.). Stamen (mag.). Stamen (mag.). Stamen (mag.). with its tail (mag.). Stamen (mag.).’ transversely, when the two cells are placed wide apart; in the Lime (fig. 336) the filament appears to bear two unilocular anthers; in the Periwinkle (fig. 337), the cells are separate and tipped by a very thick connective; in the Sage (fig. 338) the connective is greatly produced, forming a bent arm, longer than the filament, and bearing a cell at either extremity; of these cells one alone contains pollen, the other usually enlarges into a petaloid scale; in the Rosemary (fig. 339) the second cell completely disappears. The anther is often appendiculate. In the Heath (fig. 334), the appendages
345. Tulip. 346. Vitex. _ 847, Lamium. 348. Myrtle. 349. Colchicum. Pistil and andreecium. Stamen (mag.). Stamen. Stamen (mag.), Stamens. appear at the base of the cells as two small petaloid scales. In the Oleander (fig. 340) the connective is lengthened into a long feathery bristle. In the Periwinkle (fig. 337), the prolongation of the connective is large and hairy at the tip. In the Heartsease (fig. 841), the connective of two of the stamens lengthens above into a yellow, flat, triangular scale, and below into a glandular spur, which is lodged
62 ORGANOGRAPHY AND GLOSSOLOGY.
in the hollow spur of the petal. In the Pine (fig. 342), the anther is tipped by a bract-like connective. In Thuja (fig. 343), the filament bears a lateral three- celled anther, above which it dilates into a peltate disk. In the Cypress (fig. 344), the arrangement is the same, but the anther is four-celled. The anther is basifixed (a. basifiaa), when attached to the filament by its base (Wallflower, fig. 11; Tulip, fig. 345) ;—suspended (a. apicifixa), when attached by its top (Vitex, fig. 346; Lamium, fig. 347); in this case the cells often diverge, their tops touch, and it becomes difficult to decide whether they are two-celled ;—dorsifixed (a. dorsifixa), when attached by the back (Myrtle, fig. 348) ;—versatile (a. versatilis), when it rocks upon its filament, which in this case is not confluent with the connective, but attached to it by a finely pointed end (Lily, Colchicum, fig. 349).
The anther is introrse (a. introrsa), when the sutures are turned towards the centre of the flower (Campanula, fig. 319; Thistle, fig. 316; Heartsease, fig. 341) ;— extrorse (a. extrorsa), when the sutures are turned towards the circumference of the flower (Iris, Ranunculus, Hepatica, fig. 332); in these two cases the valves of each cell are unequal. The sutures are lateral when the valves are equal (Myrtle, fig. 348),
Dehiscence.— The dehiscence, or separation of the valves of each cell, may be vertical or longitudinal (a. longitudinalis), and either from top to bottom, or the reverse (Wallflower, fig. 11; Campanula, fig. 319) ;—or transverse (a. transversa), when it is horizontal, which principally occurs in unilocular anthers (Alchemilla, fig.
328) ;—-or apical by pores or slits (a. apice dehiscens), in
Sumer (ane Nightshade (fig. 350), when the sutures open above only ;— Lal or valvate (a. valuula dehiscens), when one valve of a cell ve
comes away in one piece; in Berberis (fig. 351) the posterior valve dehisces near
the connective, and ascends elastically like a trap; in Laurel the anterior valve does
this; in some Laurels with a four-celled anther, the dehiscence is by four such valves.
Pollen.—Pollen varies in different plants, but is always alike in the same species ;' its grains are commonly ellipsoid (fig. 857) or spheroid (fig. 352), but sometimes polyhedral or triangular (Ginothera, fig. 353); their surface is smooth, rugged, spinous (Rose-mallow, fig. 352), or reticulate, &c.
The ripe pollen-grain generally consists of two membranes, the <7 inner lining the outer, and containing a thick granular liquid, often ‘ mixed with minute oil-globules; this liquid, called the fovilla, is the essential part of the pollen.
As we The structure of the pollen-grains may be easily ay observed when they are moistened, which causes them to 352. Rose-matlow. burst, from the inner membrane expanding more than
. és ; 353. Ganothera, Acutpole. the outer, and rupturing the latter. At certain points of — Bive pollen,
its surface the outer membrane is thinner than elsewhere, and there folded inwards, or it presents dots which are regarded as pores. In most cases the membrane swells; at these points the fold disappears, the dots or pores enlarge, and the outer membrane bursts at the thin part; the inner membrane, thus set free, emerges from
1 To this there are many exceptions.—Ep,
THE ANDRECIUM. 63
the openings in the shape of a small tubular bladder called the pollen-tube (fig. 358) ; this again soon swells, bursts in its turn, and allows the fovilla to escape in an irregular jet (fig. 354). Sometimes the thin portions are circular, and surround a sort of cap or covering (operculum), which is pushed off by the inner membrane (Melon, fig. 355).
354. Cherry. 357. Polygala. 358. Polygala. 359. Orchis, Pollen-mass:s, Ripe pollen, 355, Melon. 356. Pine. Pollen, seen Pollen, seen separated from the ejecting the fovilla Ripe pollen Ripe pollen lengthwise from above style, with their (mag.). (mag.). (mag.). (mag.). (mag.). retinacula (mag.).
The pollen of the Cherry (fig. 354) and @nothera (fig. 353) opens by three pores, giving passage to three pollen-tubes; that of the Melon (fig. 855) by pushing off six discoid caps, which open like doors, or are completely removed by the pollen-tube. In Pine pollen (fig. 356) the outer membrane splits into halves by the distension of the inner. The pollen of Polygala (figs. 357, 358) resembles a little barrel, of which the staves, formed by the outer membrane (£), open by longitudinal clefts to allow of the passage of the inner membrane (Fr). The pollen of Orchis (fig. 359), instead of being powdery as in the previous cases, is composed of two waxy masses (masse pol- linis) supported on two small elastic stalks, named caudicles (caudiculi), and resting on a flat glandular base, called the retinaculum ; these masses present a series of small angular corpuscles (massule) joined by an elastic network, continuous with the caudicle; each corpuscle again is formed of four pollen-grains, and each pollen- grain consists of a single membrane, which lengthens into a long tube containing the fovilla (fig. 360). The retinaculum is a portion of the anterior face of the style; it secretes a viscous fluid, which agglu- tinates the originally free pollen-grains ; this viscous fluid is infiltrated between the grains, and adheres 5,.,3°) (copies. to them, then hardens, and forms the network which — »bering to the stigma. unites the grains together, and to the small stalk which bears the network (fig. 359).
The pollen of Asclepias (fig. 361) is very analogous to that of
eee. Orchis; the five bilocular anthers are introrse, and rest against the Pollen mass and gides of the stigma, which has five rounded angles ; each cell contains a compact mass of pollen, the grains of which are provided with a
single membrane, and are closely united. At each angle of the stigma, between each pair of stamens, are two small viscous bodies (re¢inacula), from each of which a furrow
64 ORGANOGRAPHY AND GLOSSOLOGY.
descends towards and abuts on the contiguous cells of two adjacent anthers. These furrows contain a soft viscid fluid, secreted by the rectinacula; this fluid extends from the retinacula to the pollen-masses; soon the two retinacula unite and solidify, and the viscid fluid in the furrows solidifying at the same time, forms a double fila- ment. This filament in hardening unites the two pollen-masses contained in the contiguous cells of two adjacent anthers, which thus form one body with the reti-
naculum, and remain suspended to it, much as the scales of a balance are suspended to the beam.
THE PISTIL.
The pistil or gynecium (pistillum, gynecium) is the whorl which crowns the receptacle and occupies the centre of the flower, of which it terminates the giowth, just as the whole flower terminates the flowering branch.
In most cases, the pistil is inserted directly on the receptacle; but in some cases the internode from which it springs lengthens, when it is called a gynophore (gynophorum), and the pistil is said to be stipitate (Fraxinella, fig. 362; Rue, fig. 363).
The leaves composing the pistils are the carpels (carpella, carpidia) ; their
number varies; they may form a single whorl (Sedwm, : Columbine, Thalictrum, fig. 364) ; or several (Trollius, fig. 365), or be solitary, by the suppression of one
362. Fraxinella, 363. Rue. 364. Thalictrum. 365. Trollius. 366. Bladder Senna. Pistil and calyx, Flower, Pistil. Pistil. Pistil.
or more (Bladder Senna, figs. 866, 367 ; Peach, fie. 368). Under certain circumstances, the suppressed carpels may be developed, and complete the whorl (Cherry, fig. 369), which has then two carpels; or, as in some Mimosas, which have
three to five, &c. The pistil is said to be mono- bi- poly-carpellary,
‘ 9 according as there are one, round or pointed, more or
less spreading scale, the
Piidourvercaly. ‘eFeagnaid endradien” pig lattes, CUBCS Of which gradually approach, and finally unite
two, or many carpels. and form a closed cavity; or, instead of uniting together, they may adhere to the
,
In the very young pistil, each carpel makes its appearance as a small
THE PISTIL. 65
edges of the contiguous carpels. The edges of the carpellary leaf (or sometimes its inner surface) present one or more small round bodies, attached to it directly or by a. cord; these are the ovules, and will eventually become the seeds; the edges or surfaces bearing the ovules are the ni placente ; the cord uniting the ovule to the placenta is the
funicle ; the limb of the carpellary leaf is the ovary; the upper portion of this limb, when it forms a slender prolongation,
i
370. Hellebore. 371. Fennel. 372. Flax. 373. Stellaria, 376. Primrose. 874. Cactus. 375. Lily.
Pistil. Pistil. Pistil (mag.). Pistil, Pistil (mag.). Pistil. Pistil.
becomes the style; the extremity or top, which is variable in form, and always formed of a different tissue, is the stigma.
In the polycarpellary pistil the carpels are :—1, entirely separate (c. distincta, Columbine, fig. 12; Thalictrum, fig. 364; Hellebore, fig. 370); 2, coherent by their ovaries at the base only, or half-way up (Fennel, fig. 371), or to the top (Flag, fig. 372; Stellaria, fig. 373); 3, coherent by their ovaries and styles (Cactus, fig. 374; Inly, fig. 375) ; 4, coherent by their ovaries, styles and stigmas, so as to simulate a solitary carpel (Primrose, fig. 876; Heartsease, fig. 877); 5, coherent by their styles and stigmas only, their ovaries being free (Periwinkle, fig. 454; Asclepias, fig. 361).
Modern botanists, in deference to old usage, have continued to give the name of ovary to the union of several ovaries, which thus form a compound ovary; they have similarly retained the names of style, stigma, placenta, for the confiuent styles, stigmas and
379, Pine. 377. Hearts- 378. Sedum. Ovuliferous scale represent placentas of several carpels. ’ ease. Carpel open ing a carpel spread out, with
is é Pistil, (mag.). neither style nor stigma. When the ovaries are free, their edges,
being folded inwards and united towards the centre of the flower, form an apparently single, but really double placenta, which, when the fruit ripens, often splits into two partially seed-bearing placentas (Columbine, fig. 13; Sedum, fig. 878). In some ‘very rare cases (Pine, fig. 379; Fir, Cypress, Thuja) the carpels remain long spread open and quite free; later they approach and their surfaces unite, but without consolidating, and they thus form closed cavities in which the seeds are sheltered. The ovary, whether simple or compound, is superior or free (ov. superum, liberum), when it adheres to none of the neighbouring organs (Lychnis, fig. 880; Primrose, F
66 ORGANOGRAPHY AND GLOSSOLOGY.
fig. 297). It is inferior (ov. inferwm) when, instead of being placed above the level of the andrcecium, corolla and calyx, it is (apparently) below them, although still
383. Gooseberry. Ovary cut _ transversely (mag.).
. : 382. Saxifrage. 884, Mignonette, 380, Lychnis. 381. Myrtle. Pistil and calyx cut Ovary cut Pistil cut vertically. Flower cut vertically. vertically (mag.). transversely (mag.),
retaining its central position (Myrtle, fig. 381). Most modern botanists explain this latter arrangement by assuming that the ovary is consolidated with the calyx-tube ; —a theory which prevailed during the first half of the present century, and the expressions ‘ovary adhering to the calyx’ and ‘ calyx adhering to the ovary’ have been employed in all Floras and descriptive works. But a closer study of the development of organs has shown that the so-called adherent calyx-tube is in reality a cup-shaped expansion of the receptacle, which has enveloped the ovary, and that the calyx only commences at the same point as the stamens and petals. Hence, what has hitherto been called an adherent calyx-tube, ought to be called a recep- tacular tube or cup. We shall return to this question when speaking of the Torus. The ovary is said to be half-inferior (ov. semi-inferuwm) or half-adherent (ov. semi-adherens), when it does not wholly adhere to the receptacular tube (Sazifrage, fig. 382). ip. In the compound ovary (whether free or inferior) the partial ovaries may bah variously united:—1, the edges touch (Gooseberry, fig. 883; Mignonette, fig. 384;
| Pree ea
=)
ES 3 cs $Y uy oy Sey fl WY i a ‘ W NEE 385. Orchis. 386. Cactus, 387. Erythreea. 589. Tulip.
Ovary cut Ovary cut Ovary cut Ovary 888. Po transversely (mag.). transversely (mag.), transversely (mag.), cut transversely. Ovary cut fea ramsélys
Gh.
Orchis, fig. 385; Cactus, fig. 8386), when their union is marked by two contiguous placentas belonging to two different carpels; the placentas are then said to be parietal (pl. parietales), and the compound ovary is one-celled (ov. uniloculare) ; 2, they are folded inwards so as to form vertical partitions, each composed of two confluent plates called septa (septa, dissepimenta), belonging to different carpels ; these septa are incomplete if they do not reach the axis of the Hower, so as to unite;
THE PISTIL. 67
the placentas are then parietal, and the ovary one-celled (Erythrea, fig. 887; Poppy, fig. 388); the septa are complete if their edges meet in the axis of the flower 3a prolongation of the receptacle sometimes traverses this axis, which then forms a column (columella: Mallow, Tulip, fig. 389; Campanula, fig. 390); through this column, whether in its origin it be receptacular, or (as is more usual) through the placentas, the nourishment of the ovules is conveyed, as well as through the carpels. When the septa are complete, there are as many cells as carpels, and the compound ovary is two- or more celled (ov. duo- pluri-loculare); and the placentas, united in 390. Campanula. : Ovary cut transversely,
pairs (two to each carpel), are central.
The septa are usually formed from the endocarp of the carpels, with an interposed expansion of the mesocarp. Spurious dissepiments (d. spuria) are vertical or horizontal septa, which are not formed by the union of the inflexed faces of two contiguous carpels; thus, in Astragalus (fig. 391), the solitary carpel is almost two- celled by an intruded vertical plate formed by a fold of the dorsal face; in Flax (fig. 8392), where there are ten septa, five project from the midribs of the carpels towards the axis, which they do not always reach. In Datura (fig. 3938), the three carpellary ovary is four-celled from the inflexed contiguous faces of the carpels, after uniting in the axis, being reflexed inwards, and meeting a prolongation from the midrib of the carpel: the placentas are thus borne on a septum composed partly of
392. Flax. ; vary cut transversely. 7 391. Astragalus, = Te reveeitini . 393. Datura. 394. Datura. 395. Wallflower. ‘Ripe pistil, five septa and Centre of ovary Top of ovary Young ovary (mag.) open. five half-septa. cut transversely. cut transversely. cut transversely.
the inflexed and then reflexed carpellary faces, and partly of a prolongation from the midrib. In the upper part of the ovary, the accessory septa (formed from the midrib) disappear, and two cells only are seen (fig. 394). In the Wallflower, and allied plants (fig. 395), the two carpels are pressed together; along each of their two edges runs a double seed-bearing fibro-vascular bundle; these are the four placentas arranged in pairs; the pistil is two-celled, by a delicate and almost transparent false septum, to which the placentas form a sort of frame. This septum is supposed to be formed by the placentas; for, when young, it is seen to be composed of four plates, which spring in pairs from each pair of placentas, and advance inwards till they join together ; later, this: false septunr appears formed of a single membrane, but it retains in the centre the trace of its double origin, in a vertical median line, along which it is easily divided without tearing.
In Coronilla and Cassia (fig. 502), the young carpel is one-celled, but at a later
F2 .
68 ORGANOGRAPHY AND GLOSSOLOGY.
period is divided into superimposed cells by septa formed of the parenchyma of the ovary, which is intruded horizontally between the seeds. ; Spurious cells (loculi spurii) are cavities in the ovary which do not contain seeds. The young ovary of Nigella presents five cells, each containing two piles of ovules ; later (fig. 396) there appear ten cells, of which five in the centre of the fruit contain seeds attached to their interior angle; the other five are exterior to these, and are empty, and due to the inflation of the epicarp (ep), which in swelling has dragged with it the mesocarp (m), whilst : the endocarp (EN) has re- mained in its place. \ Central placentas are AJA) said to be free (p. centrales, libere), when they are not united by septa to the walls
ear COMm- Paes Nigella. 398. Lychnis. = oe an > —— ¢ th 397. Crclemen: ipe ovary Young ovary (mag.) n 0) e . cut transversely. cut transversely. Pp ebe J at epen e cut vertically.
carpels; this placentation is
characteristic of Primulacee (Pimpernel, Primrose, Cyclamen, fig. 897). To explain this isolation of the placentas, it is assumed that the edges of the carpellary leaves join throughout their length, and constitute a one-celled ovary, but that their basal edges dilate, and ascend in the middle of the cell to form a central mass of placentas. The placentas of Primulacee are thus confined to the bases of the carpels. The reverse is the case in the one-celled ovary of Combretacew, where the ovules spring from the top of the cell.
In most Caryophyllee (Pink, Lychnis), the placentas appear to be free, but this arises from the early evanescence of the septa, which can only be well seen in the very young flower (fig. 398).
Some German and French botanists regard the carpellary leaf as a protective organ merely ; denying that it has the power of producing buds, and limiting this power to the floral axis. According to these, the axis alone produces ovules, and the carpellary leaves protect them. In the case of many-celled ovaries, they regard the edges of the carpellary leaves as folded inwards till they reach and cohere with the axile placentas (which in no wise belong to them), the fibro-vascular bundles of the placentas losing themselves in the tissue of the styles, which are continuations of the midribs of the carpels. In unilocular compound ovaries they consider that the placentiferous axis branches like the spokes of a half-opened parasol, and that the branches run along the contiguous edges of the carpellary leaves (Heartsease, Mignon- ette, fig. 884; Orchis, fig. 385).
This modification of the carpellary theory of placentation rests on the isola- tion of the placentas in Primulacee (fig. 397); on the enormous disproportion of the placentas relatively to the carpellary leaves in various plants (Lychnis, fig. 398; Campanula, fig. 890) ; and on the arrangement of the nerves in certain ovaries (Pea, fig. 14; Columbine, fig. 13), wherein two systems of fibro-vascular bundles are distinctly visible; the one coming from the median nerve, the others
THE PISTIL. 69
rising from the placentas, and communicating with the first; which seems to indicate a union between the axis and carpels.
The flower is isogynous (jl. tsogynus), when the carpels of which the pistil is composed equal the sepals in number (Sedum) ;—anisogynous (fl. anisogynus), when the carpels are fewer in number than the sepals (Saaifrage, Snapdragon, Comfrey) ;— polygynous (fl. polygynus), when the carpels are more numerous than the gepels (Ranunculus, Poppy).
In pistils formed of consolidated carpels, the number of the latter is determined, either by the number of styles, when these are free, or by the number of septa, or by the number of placentas, which are usually in pairs, and form vertical series, or fleshy protuberances. In pistils with parietal ovules (Butomus, Poppy, Gentian) the number of stigmas or styles or septa must be examined.
The two- or more ovuled ovary (whether simple or compound, free or adherent) is always called many-ovuled (ov. pluriovulatum). All ‘a ovaries are supposed to be normally many-ovuled, for each carpel having two placentas, and each placenta being normally one- or more ovuled, it follows that no ovary should have fewer than two ovules. A one-ovuled ovary (ov. wntovulatum) ishence youre ne tiag) “Young ovary (mag) regarded as resulting from the suppression of one —““* *tansversely. alae or more ovules. The young ovary often contains two or more ovules, of which all but one are subsequently suppressed, as in the Peach (fig. 899), which is always two-ovuled when young; and in the Horse-chestnut and Oak, which have six ovules (fig. 400). The compound ovary is usually globose or ovoid; it is lobed (ov. lobatum), when the dorsal faces of the carpels are very convex, and separated by deep furrows (usually indicating the lines of junction, fig. 225), and according to the number, it is bilobed, trilobed, &c.
The carpels are not always whorled; but are sometimes arranged in a spiral, when they form d head or-spike; the receptacle at the same time lengthening into a hemispheric, conical, or cylindric axis (Strawberry, fig. 401; Raspberry, fig. 402; Ficaria, fig. 403; Adonis, fig. 404). Roses (fig. 405) present a precisely reverse jw arrangement; the carpels (ov), instead of rising ay
At 401, Strawberry. _ 402. Raspberry. . Carpels arranged 404, Adonis. 405. Rose. Flower cut vertically. Ripe pistil, cut vertically. in a head. Pistil (mag.). Flower cut vertically.
from a plane or convex surface, spring from the walls of a cavity (c) ; which will be described under the torus. In this (exceptional) case, the carpels are said to be parietal (ov. parietalia).
70 ORGANOGRAPHY AND GLOSSOLOGY.
The compound style is improperly said to be simple (st. simplex), when wholly undivided; it is bi- tri-fid, &c., when the component styles cohere beyond the middle; bi- partite, &c., when they do not cohere to the middle. The styles of each carpel rarely bifureate once or twice ; when they do, they are double or quadruple in number to the carpels (Euphorbia, fig. 406).
The style is terminal (st. terminalis), when it springs from the top of the ovary (Apricot, fig. 411) ;—lateral, when it springs more or less from the _ st Go side of the carpel, the top of which appears bent downwards (Straw- jf f berry, fig. 407) ;—busilar (st. basilaris), when the top of the ovary is
410, Sage. 408, Alchemilla. 406. Euphorbia, 407, Strawberry. _,, 409. Comfrey. Lower portion of Carpel (mag.). Pistil. Carpel (mag.). Pistil and calyx cut vertically. flower, cut vertically,
bent down to a level with its base (Alchemulla, fig. 408). When there are many ovaries, with confluent basilar styles, the style is said to be gynobasic (st. gynobasicus, Comfrey, fig. 409), and the dilated base of this composite style, extending below the ovaries and surface of the re- ceptacle, has been called a gynobase
413, Snapdragon, 414, Dandelion.
412, Lychnis. Vertical section ofstyledurin Young pisti Young Ovary (mag.) cut trans- fertilization, eunwing WO the aL ater ace ope a versely. Ep, epicarp; End,endo- —pojjen-grains on the stigma, ing tissue, of which one is broken. carp; PL, placenta; G, ovule; TC, and the pollen-tubes pene- Car, ovary; L.c, calyx; D.é 411. Apricot. conducting tissue; ¢, septum. - trating between the cells of epigynous disk; R. raphe; Ch, Pistil cut vertically. the style (mag.). chalaza ; M, micropyle. pe
(gynobasis). The gynobase is sometimes prolonged into a gynophore (Sage, fig. 410, @) ; but a gynophore proper must not be confounded with the gynobase; the gynobasé belongs to the styles, that is, to the carpels; the gynophore proper belongs to the axis itself, of which it is the termination.!
The style is a portion of the carpellary leaf, contracted into a sort of longi- tudinal tube, filled with a moist and loose parenchyma, named conducting tissrie
1 Except under the view that the placente are productions of the axis.—Enp.
THE PISTIL. 71
(fig. 411, r); it is this tissue, which, spreading over the top or sides of the style, forms the spongy surface called the stigma (s). The same tissue descends from the style into the cavity of the ovary (fig. 412, rc), passes along the placentas (PL), and covers with its loose cells the micropyle of each ovule (¢); and it is between these cells (fig. 413) that the pollen-tube, leaving the pollen-grain on the stigma, effects a passage to and fertilizes the ovule.
In Composite, the conducting tissue consists of two threads (fig. 414, C.p, C.p), which descend from the base of the style upon the sides of the ovule, without adhering to it; at its base they join and enter the base of the funicle, near the - micropyle.
In Statice (fig. 415), according to Mirbel, the conducting tissue (tis. c) resembles a pestle; it enters the cavity of the ovary, im- mediately above the gaping micropyle of the ovule (ov.), which is suspended from a basal cord (cor.). This conducting tissue rests on the micropyle like the stopper of a decanter, and is visible after fertilization (fig. 416).
Pistil.
z/} NW Reals
420. Melon. Stigma.
415. Statice. ee 4S Ova cut vertically, 416. Statice. 421, Rumex. 422, Parietaria. 418. 419. : shawn the ovule before Fertilized Pistil (mag.). Pistil (mag.). Tobacco. Wallflower.
fertilization (mag.). ovule (mag.). Pistil. Pistil (mag.).
The stigma (figs. 413 and 411 s) is nothing but the conducting tissue spread out; the stigmatic surface has no epidermis, and is usually spongy, damp, and papillose, and thus suited to retain the pollen.
The stigma (whether simple or compound) is complete (st. com- pletum) when it is continuous with the style, and clearly distin- guishable. The complete stigma may be globular (Daphne, fig. 417), hemispheric (Primrose, fig. 376), round (Tobacco, fig. 418), forked (Wallflower, fig. 419), bi-lamellate (Datura), lobed (Lily, fig. 375; Melon, fig. 420), lacuniate or & fringed (Saffron, Rumex, fig. 421), penicillate (Parietaria, fig. 422), plumose (Wheat, fig. 423), discoid, conical,cylindrie, club-shap ed, awl-shap ed, &e. 424, Vetch. 425. Ranunculus. 423. Wheat.
It is superficial (st. super- Pistil. | Carpel (mag.). Flower (mag.). ficiale) when confined to the surface of a part of the style or ovary, and only
72 ORGANOGRAPHY AND GLOSSOLOGY.
distinguishable by its papille. The superficial stigma is terminal in Frawinella (fig. 362), Strawberry (fig. 407), Sweet Vetch (fig. 424); lateral in Ranunculus, where it is hooked (fig. 425) ; and in Hearts- : [=
ease (fig. 377), where it forms a hollow ball with a two-lipped
429, Lychnis. Pistil.
f
428, Orchis. Flower without the ovary. 430, Coinflower, 426. Polygala. st, stigma ; R, retinaculum; P, pollen; Style and stigmas Pistil. 427, Iris. Pistil. L, anther-cell (mag.). (mag.).
orifice; and in Polygala (fig. 426), where it forms a small very short lip (Sti.) on the sides of a style (Sty.) hollowed into a funnel, and spoon-shaped at the end ;— , in Iris (fig. 427),in which the composite style divides into three petaloid plates with two unequal lips, the interior # of which is bifurcate, the stigmatic surface (Stig.) occu- pies a small transverse fissure between these lips;— in Orchis (fig. 428), where it forms a shining and viscous cup (st) situated below the retinaculum (8) ;—in Lychnis (fig. 429) where it is papillose and transparent, clothing
431. 434. Achillea, 435. Achillea. 436, Achillea. Chrysanthemum. 432, Eupatorium. 438, Achillea. Semi-floret Style of a floret Style of Pistil (mag.). Pistil (mag.). Floret (mag.). (mag.). (maz.). a semi-floret (mag.).
the furrowed inner faces of the styles;—in Plantain, where its papillae form two velvety lines along the style.
The stigma must not be confounded with certain peculiar hairs which some- times garnish the style, and are almost always directed obliquely upwards, and intended to catch the pollen; they are most. frequent in flowers with contiguous.
THE PISTIL. 73
introrse anthers. In these plants the young style is much shorter than the stamens; it grows rapidly as the flower expands, and traverses the tube formed by the stamens, where its hairs, rubbing the anther-cells, open them, and sweep out the pollen which adheres to them; they are hence called collecting hairs or brushes (pili col- lectores). In the Cornflower (fig. 430) the stigmas (Sti.) are lateral and superficial, as in the Lychnis, and below them is a small swelling clothed with a tuft of very small collecting hairs (pc). In the Chrysanthemum (fig. 431), the two style-branches are papillose on their inner faces, and tipped by a little tuft of collecting hairs. In Eupatorium (fig. 432) the two style-branches are cylindric and bristle with collecting hairs ; and the stigmatic surfaces form a little band which extends from the fork half-way up the branches. In Achillea (figs. 483, 434), the heads of which are rayed, the central florets are tubular and hermaphrodite (fig. 4383), and the circumferential are female semi-florets (fig. 434). Here the style-arms of the central florets (hermaphrodite) are papillose on the inner face, and tipped with a brush of collecting hairs; the semi-florets again, being female only, their style-arms (fig. 436) have no collecting hairs (fig. 435), but, as the pollen of the centre florets may reach them, their style-arms are papillose, so as td retain the pollen and secure fertilization. In Campanula the five style-branches (fig. 437) are papillose on the inner face, and subtended by five rows of collecting hairs, each row being double, and answering to the two halves of each anther. Before expansion, the style grows rapidly, the { anthers open, and their pollen-grains, which bristle / with hooks, adhere firmly to the hairs which have
swept them; this accomplished, the collecting
——
tee
Mp ARR
0S
a vr
re .
SZ
407. Campanula, aracien amd vistil (mag.). -‘Pistil(mag),Pistil and calys (mag. aed hairs are retracted within themselves, like the horns of a snail; the pollen then disappears, and the style becomes clean, its surface being merely a little rough.
The stigma is sessile (st. sessile) when, there being no style, it is seated directly on the ovary. In the Tulip (fig. 845) it forms three bi-lobed crests ;—in the Nettle, a pencil ;—in Arum (fig. 438), a little papillose tuft ;—in the Vine- (fig. 439), a flat- tened head;—in the Elder (fig. 440), three rounded lobes ; in the Poppy (fig. 441), velvety radiating double crests, clothing the depressed styles, which together resemble a shield or cap with scalloped edges.
The stigma is sometimes absent, and then the ovary remains open; this is the case with Pine (fig. 379), Cypress, and Thuja, the female flowers of which are arranged in a spike; each is furnished with an outer bract, which soon withers and disap- pears; each is formed of a scale representing an. open carpel, without style or stigma,
74 ORGANOGRAPHY AND GLOSSOLOGY.
bearing at its base two ovules with a gaping micropyle; after fertilization, these carpels thicken, harden, and become appressed, and form closed cavities which protect the seeds during their ripening.
TORUS, DISK, NECTARIES.
_ The torus is the (part of the receptacle situated between the calyx and the pistil on which the corolla and androecium are inserted. It is merely the periphery of the receptacle, and not a special organ; but for convenience of description it is so considered. :
The torus produces, besides stamens and petals, nectariferous glands and sundry
442, Columbine.
Pistil surrounded by 443, Tree Peony. 444, White Water-Lily. _ 445, Orange.
scales. Torus showing Flower without the corolla Pistil and cup bearing the petals Vertical section of pistil the scars left by and most of the stamens, and stamens. and receptacle,
the stamens (mag.). T, torus ; C, calyx.
expansions analogous to petals or stamens. Thus, in the Columbine (fig. 442), between the andreecium and the pistil, are ten membranous silvery white scales, with folded edges, larger at the base than at the top, which may be considered as filaments, and which sometimes bear an anther at their extremity. In the Tree Peony (fig. 443), the thick swollen torus elongates into a membranous cup surrounding the carpels, without adhering to them, and open at the top to afford a passage to the stigmas: it appears to form a part of the fruit, from which it is nevertheless very distinct. This petaloid involucre sometimes bears anthers. In the White Water Lily (fig. 444) the stamens and petals cohere with the torus, which envelops the ovary, so that they appear to adhere to the ovary; they die after flowering, leaving the torus marked with their scars. In the Yellow Water Lily, the thick cup, externally green and
Flower withetcrna flaccid, which some botanists have considered as a torus envelop-
(mag.).
ing the ovary, is nothing but the epicarp of the ovary; at maturity it bursts irregularly, and comes away, leaving the seeds retained by the endocarp, when they fall to the bottom of the water and germinate.
The torus often forms, below the ovary, a projecting ring or swelling, from which spring the stamens and petals (Orange, fig. 445 7; Mignonette, fig. 446); but more often this ring, reduced to its most simple form, only appears as a circular line
TORUS, DISK, NECTARIES. 75
on the receptacle, between the pistil and the calyx (Chelidoniwm, fig. 447). . In every case the andreecium and corolla, being inserted on this ring and below the pistil, are hypogynous, and the plant thalamifloral if the petals are free, corollifloral if they are coherent.
In many plants the receptacle dilates into | a cup, which represents a calycinal tube, over which the torus is spread, and the stamens and pistils spring from its outer margin (Strawberry, fig. 401; Apricot, fig. 449). In others it rises upon the carpels, envelops them oane ton ok 447. Chelidonium, 449. Apple. clos ely, and forms with transversely. Pistil (mag.). Fruit cut vertically. them but one body, upon the circumference of which the stamens, petals and calyx are inserted at a higher level than the ovary (Myrtle, fig. 381; Sawifrage, fig. 382). This cup, enveloping the carpels and formed by the growth of the receptacle, is the calyz-tube of modern Floras, which it would be better to call a receptacular tube or cup.
This hypertrophy of the receptacle is particularly striking in orchard fruits. If we halve an unripe pear or apple (fig. 448), we find five carpels, forming five two- ovuled cells, surrounded by a fleshy mass, the so-called calycine-tube (better called receptacular cup), which has closely enveloped them, and agglutinated them by their lateral faces, but left their inner edges free. A vertical section of a ripe apple (fig. 449) exhibits a fibro-vascular bundle, extending from the peduncle, with which it is continuous, to the carpels (F) ; it is the parenchyma of the receptacle, which has here enormously increased in bulk to envelop the ovaries (t); at the summit of this mass, that is to say, at the top of the fruit, the remains of the sepals and stamens may be seen carried up by the expansion of the receptacle.
The receptacular theory of the calycine-tube completely explains the arrange- ment of the carpels of a Rose (fig. 405). In this, the position of the carpels on the internal wall of a calycine-tube was difficult to admit; the whorls of the flower being lateral expansions of the axis, it was impossible, in defiance of the law of the evolution of floral whorls, to attribute to the calyx the power of producing carpels. The position of the coloured ring from which the petals and stamens rise is the key to the apparently abnormal position of the carpels; this ring surmounts the ovoid body enclosing the carpels; the torus has therefore reached that point before emit- ting laterally the petals and stamens; and since the torus is nothing but the circumference of the receptacle, it is evident that it must be the latter organ which constitutes the hollow body enclosing the carpels. In fact, the maeoptacle, instead of forming, as in the Strawberry (fig. 401), a hemisphere, has swollen, risen much above its ordinary level, and formed a sort of cup; thus resembling the finger of a glove turned inside out, the normally outer or convex surface becoming thejinner, or concave, one. Were the convex receptacle of the Strawberry reduced to a thin
76 ORGANOGRAPHY AND GLOSSOLOGY.
membrane, and turned inside out, the sepals would then form a ring round the mouth of a sort of bottle, represented by the inverted receptacle, whose throat would be occupied by the stamens and petals, and its inner surface by the ovaries; and the strawberry would be thus changed into a rose. The last evidence of the hollow body of the rose being a cup-shaped expansion of the axis rests on the cases in which the receptacle forms, instead of a cup, a central convex projection, which bears carpels; the rose thus being converted into a strawberry.
In all these cases the plant is calycifloral; the stamens and petals are not hypogynous, as inthe Lychnis (fig. 880) and Primrose (fig. 297), but are inserted above the base of the pistil, at the distal end of the torus (Sumach, fig. ne or on the outer circumference of a ring or cup formed by the torus (Circa, fig. 450 bis; Alchemilla, fig. 451); they are thus either perigynous or epigynous, accord-
451. Alchemilla. 450, Sumach. 452, Nasturtium.
Flower cut vertically (mag.), Flower cut vertically (mag.). Flower cut vertically. ing to their insertion around (fig. 450) or above the ovary (fig. 450 bis). When the torus both spreads over the base of the calyx and around that of the ovary, the andrecium may be hypogynous, and the corolla peri- gynous; this is very rare, but occurs in Tropeolwm (fig. 452),
The term disk has been reserved for the tumid ring which, in hypogynous flowers, surrounds the base
4.9 bis Cirewa, 453. Radish. 455. Sedum, 457. Parnassia,
Flower cut Pistil Pistil and Petal nee ee 454, ce vertically. and nectaries. nectaries (mag.). and nectaries, petal and nectary. and nectaries.
of the ovary (Orange, fig. 445); and for the thickening which crowns the inferior ovary, enclosing the base of the style (Circea, fig. 450 bis). These thickenings of
ARRANGEMENT OF APPENDICULAR ORGANS. 77
the torus are glandular, and usually secrete honeyed fluids, whence they have been classed with nectaries, of which we are about to speak.
Nectaries or nectarjferous glands are usually developed from the torus, and placed upon it or the organs developed from it.
The receptacle of the Radish (fig. 453), Wallflower (fig. 10), and other Crucifere, bears four or six glands ;—-the Periwinkle (fig. 454) two;—Sedum (fig. 455) five ;— most Gesneriacee also five; but in this Order all intermediates between five free glands and a large hypogynous or epigynous disk are to be found. In the Straw- berry (fig. 401), Peach (fig. 868), and other Rosacee, the orange-yellow layer of the torus, which is spread over the calyx, secretes superficially a honeyed liquor; but often for so short a time that it is difficult to observe it. In Ranunculus (fig. 237) a small neetary occurs, protected by a scale, at the base of the claw of each petal. In Berberis (fig. 238), each petal bears, a little above the base, two naked ovoid necta- ries. In the Fritillary (fig. 456), the six petaloid perianth-segments each bear a nectary a little above the base, which, instead of projecting, forms a furrow. In the Lily, a double nectariferous furrow extends along the face of the midrib of each petal. In Parnassia (fig. 457), opposite each petal there is a petaloid scale which ramifies into three, five, seven, nine, or fifteen branches, each tipped by a globular nectary. =
Nectaries are sometimes on the tip or base of the connective of the stamens, as in Adenanthera, Prosopis, &c. In Heartsease (fig. 458), two nectaries pro- ceed from two of the stamens, and, projecting from the connective at the base of the anther, form two recurved tails, sheathed in the hollow horn of the lower petal, at the base of which they secrete a sweet liquor from their tips.
It has already been remarked that hollow petals contain a nectary in their cavity (Columbine, fig. 246; Aconite, fig. 247; Nigella, fig. 244; Helle- ya ea
_ bore, fig. 248; Winter Aconite, fig. 244 bis). acne:
In monopetalous corollas the nectaries may be superficial (Honeysuckle, Lilac), or occupy a cavity which externally forms a boss or spur (Linaria, fig. 286; Snap- dragon, fig. 285; Centranthus, fig. 291); in the latter case the corolla is irregular, and the stamens are often imperfect; but it is difficult to say whether the necta- ries are the cause or effect of this irregularity.
Nectaries are not confined to the torus; they are found on the external surface of the calyx in Malpighiacee; and a glandular secreting layer occurs in the thick- ness of the septa of the ovary of Liliacee, named by Brongniart ‘ glandes septales.’ In unisexual flowers, it often happens that the absent organs are-replaced by necta- ries (Melon, and many other diclinous plants).
ARRANGEMENT OF APPENDICULAR ORGANS AROUND THE AXIS.
Appendages or appendicular organs are lateral developments from the vegetable axis :—the leaves, bracts, sepals, petals, stamens, and carpels.
It has been stated (Introd. p. 2), that leaves are either opposite, whorled, or
78 ORGANOGRAPHY AND GLOSSOLOGY.
alternate; as also (p. 42) that the floral organs (calyx, corolla, androecium and pistil) are normally whorled; but we have warned the reader that very frequently the leaves of each series, instead of forming a true whorl, are arranged in successive flattened. spirals, though still retaining the name of whorls.
We will now advert somewhat in detail: 1. To the arrangement of leaves properly so called, carpellary leaves, and bracts (this branch of Botany is called Phyllotaxy) ; 2. To the arrangement of the petals and sepals, an arrangement termed Vernation, because it can only be satisfactorily studied before the flower |
expands. PHYLLOTAXY.
When leaves are clearly whorled, either in twos (opposite), threes, fours, fives, &c., they are generally separated by equal intervals, and consequently the arc com- prehended between the bases of two contiguous leaves is equal to the circumference of the stem, divided by the number of leaves in the whorl. This are will therefore embrace half the circumference if the whorl consists of two leaves; one-third of the circumference if it consists of three; one-fourth, one-fifth, one-sixth, if it consists of four, five, or six leaves.
It has also been observed that the leaves of a whorl are not placed directly above those of the whorl immediately above or below them, but opposite the intervals which separate the leaves, and either exactly opposite, or to one or the other side of the interval. When the leaves are opposite, and each pair crosses the upper and lower pair at right angles, the leaves occupy four rectilinear lines, and, seen from above, form a cross; such leaves are decussate (f. decussata). Whorls of three or four leaves will in like manner occupy six or eight longitudinal lines. Whorled leaves are relatively few; many more plants have opposite leaves, and by far the largest number have alternate leaves; and it is by the lagter that the arrangement of leaves on the stem must especially be studied.
We have seen (p. 8) that the Oak presents five leaves (I, 2, 8, 4, 5), spirally arranged around the stem, so that the one (6) which succeeds the- fifth is placed vertically above the first. In a longer branch, the seventh would be placed above the second, the eighth above the third, &. This spiral arrangement prevails in many woody and herbaceous plants, as the Peach, Plum, Cherry, Rose, Raspberry, Hawthorn, Spirea, Cytisus, Poplar, Willow, Sumach, Wallflower, Mignon- ette, Heartsease, Groundsel, Poppy, &c.
The naturalist Ch. Bonnet, who was the first to observe this arrangement of alternate leaves, rernarked that their points of insertion were separated from each other by equal intervals, and discovered some more complicated arrangements, as that, instead of the sixth leaf, it is often the ninth or even the fourteenth which is placed vertically above the first, indicating a series of eight or of thirteen leaves. Modern botanists have followed up this subject, and have formulated as laws the facts which Ch. Bonnet had not generalized.
To begin with the simplest example of alternation of leaves, that in which the leaves alternate on opposite sides of the stem (Lime, Ivy, Elm, Hazel, &.): if a
PHYLLOTAXY. 79
thread be carried round the stem so as to touch the insertions of these leaves, it will describe a regular spiral. If one of these leaves be taken as a starting point, and if they ‘be counted from below upwards, it will be perceived that 3 is above 1, 4 above 2, &c.; and all are arranged on two equidistant vertical lines, being separated by half the circumference of the stem. Leaves thus placed are called distichous (fig. 69).
If three leaves complete one turn of the spiral, the fourth will be vertically above the first, the fifth above the second, &c., and all will be arranged on three equidistant vertical lines, and separated from each other by a third of the circum- ference of the stem. Such leaves are termed tristichous (Galingale, Carex, and many | monocotyledons).
In the Oak, Poplar, Plum, &c., where the leaves are arranged in fives, and occupy five vertical equidistant lines on a branch, these lines divide the circum- ference of the branch into five equal portions, and are separated by an are equal to one-fifth of the circumference of the stem. But here it is important to remark, that if, taking one of these leaves as the starting-point, we examine the successive leaves of the spiral, the leaf which follows or precedes number one is not situated on the nearest vertical to that to which number one belongs, but on that which comes after number two, and that this vertical is at two-fifths the circumference from the first. Here the spiral is not completed in one turn by two or three leaves, as in the two preceding cases; for the intervals between the five leaves are such that, before arriving at the sixth, which is immediately above the first, the spiral passing through their points of insertion would make two complete turns round the stem; the distance between the leaves will therefore be two-fifths of the circumference. This arrangement is called the quincynx.
The name cycle is given to a system of leaves in which, after one or more turns of the spiral, a leaf is found immediately above the one from which we started, and beginning a new series. To obtain a complete idea of the cycle, we must therefore consider, besides the number of leaves which compose it, the number of spiral turns they occupy.
The angle of divergence of two consecutive leaves is measured by the arc between them. Thus the fraction 4 expresses the angle of divergence of tri- stichous leaves, and the fraction 2 the angle of divergence of quwincunz leaves. As to distichous leaves, the term angle cannot apply to their divergence, being half a circumference, but it is expressed by the fraction 4. These fractions have for their numerator the number of the spiral turns of which the cycle is composed, and for denominator the number of leaves in the cycle, or, to speak more exactly, the number of spaces separating the points of insertion of these leaves. A cycle may therefore be designated by the fraction expressing the angle of divergence, since the denominator of this fraction indicates the number of leaves, and its numerator the number of turns.
Besides the three cycles mentioned above, designated by the fractions 3, 3, 3, we find cycles of eight leaves in three turns, ie. $; thirteen leaves in five turns, +’; ; twenty-one leaves in eight turns, 3; thirty-four leaves in thirteen turns, $3;
80 ORGANOGRAPHY AND GLOSSOLOGY.
fifty-five leaves in twenty-one turns, 21; eighty-nine leaves in thirty-four turns, 34; one hundred and forty-four leaves in fifty-five turns, 735;, &e.
Now, if we arrange this series of fractions progressively,
a oh 28 Bb. 8B S$. 2:4. 55 3, 4, $ 8, oo fp HL Hh OH, HD, &e.,
several curious analogies will appear, of which the most striking is, that each frac- tion has for its numerator the sum of the numerators of the two preceding fractions, and for denominator the sum of the two preceding denominators. In like manner any one of these fractions may be obtained by taking the two fractions which imme- , diately follow it, and finding the quotient of their numerators and denominators. It is easy to obtain these fractions when the leaves are neither too distant nor too crowded on the stem, as often happens. The spiral which takes in all the leaves is called a primitive spiral. But if the internodes are long, the leaves consequently remote, and the cycle composed of a considerable number of leaves, it becomes diffi- cult to ascertain by inspection which leaf is vertical to the first, and hence to esti- mate the angle of divergence be- tween two con- Sn secutive leaves. oe “sy This becomes still
pa i — more difficult when
4 Be the leaves are eee | a x crowded, as in the ae as rosettes of the f Sus Houseleek, in Plan- ae ae tains and other Ln \h\ so-called stemless 13) hace y plants, in the a SI bracts of heads NS i (Artichoke) ; or in ‘aj * v, the scales or open
5 agi oe af carpels which com- < a pose the cones a > of Pines, Firs,
Larches, &c.
In the case of crowded leaves, we can, however, by a very simple calculation, ascer-
459a. Primitive spiral from right to left, and bearing three cycles, each of eight leaves, shown by the m numbered points, and inserted on three turns of the spiral. The secondary spirals, formed i the tain the angle of
right by the numbers in fives, are indicated by the finely dotted lines; the secondary spirals. iv formed to the left by the numbers in threes, are indicated by the lines - - - -- p is e div ergence, and thus determine the
primitive spiral. Take, for example, a stem bearing a series of cycles of eight
PHYLLOTAXY. 81
leaves moderately separated on three turns. of the spiral; the cycle will be easily recognized, and the expression of the angle of divergence will be 3. This arrange- ment obtains in many succulent plants, and especially in Sedum Telephium. Suppose the stem to be shortened, so that the leaves become crowded into a rosette, it follows that the spiral will become a very close one, comparable to a watch-spring of which the coils contract in approaching the axis (fig. 459 c). Let us suppose, further, that the inner end of this spring represents the top of the spiral, and its outer extremity the base; it is obvious that on this depressed spiral the leaves nearest the centre would have been the nearest to the top of the more open spiral, and those nearest the circumference would have been the lowest. Now, knowing the angle of divergence of the leaves of Sedum in a normal state, it remains to find it for the same leaves gathered into a rosette ; for this it suffices to represent or plan three or four cycles, of three leaves each, according to the fraction 2, that is, each cycle to contain eight leaves, that shall occupy three turns of a right-to-left spiral, and be separated by an arc equal to $ of the circumference (fig. 459 a). A circle must then be drawn around this spiral, of which the radius shall join the two extremities of the spiral; it is by means of this circle that we must be guided in laying down the angular divergence of the leaves, which being 3, it follows that the circle must be divided into eight equal portions by as many radii, when three of these portions will represent 2 of the circumference, or in other words the angle of divergence. This done, we place a number (1) on the position of the first leaf, which is where the spiral touches the circumference; then follow the coils of the spiral, and after clearing the three first arcs (3 of the circumference) indicate the position of the next leaf (2), which will be at the intersection of the spiral and radius which bounds the third arc; and so on, a leaf position being marked at the intersection of every third radius with the spiral; till the centre of the spiral being reached, the plan will represent the entire series of leaves, numbered in order.
Let us now examine the relative positions of the leaves, as indicated by their numbers. If we examine the radius bearing leaf No. 1, we shall see above it on the same radius, Nos. 9 and 17, the difference between which is eight, and it is obvious that this horizontal radius would represent a vertical line on the Sedum stem, along which the leaves 1, 9, and 17 are inserted, each marking the commencement of a cycle; as also that these leaves are separated by three turns of the spiral. Com- mencing at any other radius (say Nos. 2, 10, 18, d&c.), the result is the same, the fraction 3 being clearly expressed. ae
There are other relations between these leaves, which this plan clearly demon- strates. Thus, between Nos. 1 and 4, situated on the next radius to the left, there is a difference of three; the same between 4 and 7, &c.; and starting from leaf No. 2 or 8, we shall find the same numerical relations as in the first instance; the number expressing the difference (3) being the same as that of the series. If we now draw a line through the positions of all the ‘leaves of each series, we shall see that each line is a portion of a spiral, and that these three partial spirals take the
@
82 ORGANOGRAPHY AND GLOSSOLOGY.
same direction, and include within their course the points of insertion of all the leaves.
If, on the other hand, starting from No. 1, we examine its relations with No. 6, on the radius next to the right, we find between them a difference of five; and similarly with 6 and 11, 11 and 16, &.; and between Nos. 2 and 7, and Nos. 12, 17 and 22, and along the series commencing with 4 and 5. Here again, from left to right, the number expressing the difference corresponds to that of the series. Each of these series may be shown more clearly by means of a curved line uniting all the leaves which compose it, and we shall then have five segments of a spiral turning symmetrically from left to right, and passing through the insertions of all the leaves. These segments of the spiral have been termed secondary spirals, to distinguish them from the primitive spiral, also termed generating spiral. Now it will be remarked that the secondary spirals proceeding from right to left are three
459.c. Rosette forming a cycle of thirteen leaves, of
459 6, Rosette forming two cycles of eight leaves, which the angle of divergence is ,%; the axis A, Where
of which the angle of divergence is 3. they are inserted, bears five turns of the spiral, show-
ing the point of insertion of each leaf. in number, which number is the numerator of the fraction 3; and that the sum of these three, and of the five going from left to right, is eight, or the denominator of the fraction. Iftherefore it is possible to count the secondary spirals to left and right, of rosettes, involucral bracts, or scales of Pine cones, in all of which the primitive spiral is obscured by the closeness of the parts, we may assume that the smaller number represents the numerator, and the sum of the two numbers the denominator of the desired fraction; which again gives the angle of divergence, the number of leaves in the cycle, and the number of turns of the spiral which they occupy. :
This crowding of the leaves, which we have illustrated by Sedum, is frequent amongst plants with radical leaves, in many of which the cycle of the leaves is indicated by the fraction 2 (Common Plantain, fig. 459 b).
The number of secondary spirals to right and left being known, it is easy to number each leaf in the primitive spiral. Take, for example, the rosette (fig. 459 c), which represents a Houseleek, or the cone of the Maritime Pine (fig. 459 d). Their
PHYLLOTAXY. 83
angle of divergence is -3,, which is easily found by counting the very obvious secondary spirals to right and left. We have only alluded to the most obvious secondary spirals ; but it will readily be understood that there are many others, some more, some less oblique than these, and that every numerical series having the same relative differences between them would be a spiral. The secondary spirals are especially visible in Pine cones, the axis of which is much longer than that of the Houseleek, and in which they form very distinctly marked parallel series.!
Begin by numbering as 1 one of the outer leaves of the rosette, or of the lower scales of the cone, and regard it as the first of a secondary spiral turning from left to right. To find No. 2 on it, re- member that the numbers of a secondary spiral must be separated by a space equal to the number of the secondary spirals of which this forms a part; and as there are five parallel left-to-right spirals, the second leaf or scale must be numbered 6, the third 11, and so on to the top of the cone, or centre of the rosette. Having thus numbered all the scales or leaves of one of the five parallel secondary left- to-right spirals, these numbers may serve as start- ing-points from which to number all the other scales or leaves of the cone or rosette. We know that each of the numbered scales or leaves of the secondary left-to-right spiral equally forms aibaceh, decceting tq Wat acan ee one in the series of the right-to-left spirals, and we ——_fo'the right by the series of numbers in irony may number all the leaves or scales from any — “™’ st bY he*eties ol nunbers in cights starting-point, by adding 5 when turning to the right, and 8 when turning to the left.
Let us take, for example, No. 82; this number in the left-to-right spiral would (adding 5) lead us to No. 37, 87 leads to 42, and so on; but since No. 32 also enters into one of the eight secondary right-to-left spirals, the leaf or scale succeed- ing it in this spiral should be numbered 32 +8, i.e. 40; and following this spiral, by additions of 8, we should have 40, 48, 56, 64, 72, &c.
To obtain in the same spiral the numbers below 32, we must deduct the number 8, which we had before added, and we shall have successively 32, 24, 16, 8.
If, in starting from the same No. 32, we descend the secondary spiral which turns from left to right, we must take 5 from 32, when we shall have successively 27, 22, 17, 12, #5 2, &e. ' :
All the Ieaves or scales of the rosette or cone being numbered, their succession
1 Nothing is easier than to observe this, by numbering the scales of a ripe cone of the Maritime Pine.
a2.
»
84 ORGANOGRAPHY AND GLOSSOLOGY.
indicates the generating spiral. But the direction of this generating spiral from left to right, or right to left, depends on the angle of divergence; if the fraction be 3, or 3, or $4, and so on, the primitive or generating spiral will follow the most nume- rous secondary spirals; but if the fraction be Z,or #, or H, &c., the generating spiral will follow the least numerous secondary spirals. :
Take, for example, the fraction 4 (fig. 459 a), and let us examine the relation be- tween the genera~- ting and secondary spirals. Whatever may be the direc- tion of the genera- ting spiral, the least § numerous secondary spirals must follow the same, and vice versd. Suppose the spiral to be aright- to-left one, as in 459 a, it follows that, placing No. lp 1 where the radius
touches the: outer end of the spiral, and successively numbering the leaves from 3 to 3, the nearest radius to the left will be occupied by a leaf ee before the nearest + hue uemberod pelnte: aaa lostial ta ie tarne of the Speal’ ‘the secondary spirals, formed to te TAdiUS to the right.
right by the numbers in fives, are indicated by the finely dotted lines; the secondary spirals, formed to the left by the numbers in eights, are indicated by the lines - ----- ; The first leaf on
the left radius will evidently be No. 4; for it will occur after traversing three $ (2); that is, after one entire revolution, plus 4, and consequently on the left-hand radius nearest the one from which we started. The leaf which will be found on the right radius will evidently be No. 6, for it will occur after five times 3 (+9), that is, after one re- volution minus 4, and consequently on the nearest right-hand radius. Now we know that the number of secondary spirals is equal to the difference between the numbers of two consecutive leaves on one of these spirals; therefore, if we suppose the fraction to be 3, the number of the secondary spirals from right to left, that is, of
‘the secondary spirals which follow the direetion of the generating spiral, will be less
PHYLLOTAXY. 85
than the number of the secondary spirals which follow an opposite direction. The same result can be obtained from the succeeding fractions.
On the contrary (fig. 459 e), with the fractions £, 5, 13, and so on, we find that the right-hand radius is occupied by a leaf sooner than the left-hand one, and that in consequence the number of the first leaf on the right-hand radius is less than the number of the first leaf on the left-hand radius. Therefore the number of secondary. spirals which can be followed from left to right is less than those from right to left, or, in other words, the most numerous secondary spirals turn in the same direction as the generating spiral, and knowing the direction of the one, we know the direc- tion of the other.
The direction of the generating spiral varies not merely in the individuals of a species, but sometimes in the same individual. Thus, in cones from the same speci- men of Maritime Pine, right-to-left secondary spirals will be more frequent in some, and left-to-right in others; but in all cases the relative direction of the generating spiral follows the law just enunciated.
The angle of divergence itself is constant only in the fractions 1, 1, 2, and when these cycles are more numerous, the one is often substituted for the other, which is owing to the distance between them being extremely small, and to the fact that the angles expressed by the fractions -2,, $,, 13, 24, 24, &e., if reduced to degrees and minutes, differ by a few minutes only; so that the angles of divergence actually oscillate between 137° and 188°. A slight twist of the stem or axis is sufficient to account for so small a variation, and may well occur in rosettes of leaves, in involucral bracts, and in cones, and cast a doubt on the value of the angle of divergence. Thus, in Pines (fig. 459 d), the rectilinear series indicating the suc- cessive cycles may deviate more or less to right or left, so that the secondary spirals, which were the most obvious at the base of the cone, become less so in ascending, and render it difficult to determine such fractions as 4, =4,, 8. A change in the shape of the stem will also lead to the substitution of one cycle for another, as in certain Cacti with ribbed or angular stems bearing tufts of prickles, and whose ribs double as they ascend, and offer cycles of a higher number.
Lastly, there are exceptional cases which perplex the student of Phyllotaxy; the above-named fractions are not the only ones which may be observed; 4, 4, 2, =3;, &c., do occur, though very rarely ; but when they do, they preserve among them- selves the same relations as the preceding, i.e. that each successive fraction may be obtained by the addition of the numerators and denominators of the two preceding. We have seen that whorled leaves present a succession of circular groups; but here also, as in alternate leaves, the spiral arrangement is discernible. In a branch of Oleander, for instance, where the leaves are whorled in threes, a relation exists — between any three vertically superimposed leaves of successive whorls; and a line successively passing through their insertions will describe a regular spiral; and if we examine the relations between the other leaves of these whorls, we shall perceive that the number of whorls represents as many parallel spirals as there are leaves in
each of them.
86 ORGANOGRAPHY AND GLOSSOLOGY.
AESTIV ATION.
Aistivation (prefloratio, wstivatio) is the arrangement of the floral organs in the bud, and is of especial importance in respect of the calyx and corolla.
The leaves of each floral whorl may be inserted exactly at the same level (forming a true whorl), or at unequal heights, when they form a depressed spiral, the lowest leaf of which is necessarily the outermost. The true whorl presents two modes of estivation—the valvate and the contorted.
1. Aistivation is valvate (e. valvaris) when the contiguous edges of the parts touch throughout their length, like the two leaves of a door (460 a); and it is then nearly always regular. Itis induplicative (ce. induplicativa) when the contiguous parts cohere by a part of their back; reduplicative (e. reduplicutiva) when by a part of their faces
e
Ormra1@y(
wae <4
460a. Valvate 460d. Valvate 461. Valvate 462. Contorted 463. Imbricate eestivation. induplicative estivation. reduplicative estivation, eestivation. estivation.
RV, 1
(fig. 461). 2. Aistivation is twisted or contorted! (contorta) when the leaves are so placed that each leaf partially covers one of the two between which it is placed, and is similarly covered by the other, as if each were twisted on its axis (fig. 462) ; in this case the whorl is always regular.
The depressed spiral presents two modes of estivation: the imbricate, properly so called, and the quincuneial. These two are often indifferently termed imbricate. 1. In the true imbricate estivation (e. imbricativa, fig. 463) the parts (usually five) successively overlap, from the first, which is wholly exterior, to the last, which is wholly interior, and placed against the first; they thus complete one turn of a spiral. In quincunsial estivation (@. quincuncialis) two of the five pieces are exterior, two interior, and one intermediate, one side of the latter being covered by one of the outer, and on the other covering one of the inner (fig. 464). This arrangement corresponds to that of leaves expressed by 2. To explain this estivation, which is nothing but a depressed spiral with two coils, we must consider the axis of the flower as a truncated cone, and draw a spiral line twice round it, from bottom to top; then mark off on this line five equidistant points, so that a sixth point at the top of the cone will be immediately above the first; it is clear that the interspaces will equal 2 the circumference of the cone, and the five spaces between the six points will constitute 19, i.e. twice the circumference; which equals the two turns of the spiral traced on the conical axis of the ‘flower. Now substitute for the five points five sepals or petals which shall be large enough to overlap; then depress the cone to a plane, and we shall have two exterior leaves (1, 2), a third,at once half
1 Also called convolute by various botanists.—Ep,
AESTIVATION. 87
interior and half exterior (3), and two wholly interior (4, 5), which are both nearest to the top of the cone, and the most central. The Rose calyx (fig. 465) confirms this view ; its outer sepals being next the axis of the flower, and consequently most vigorously developed, present small lateral leaflets, and often a terminal true leaflet, thus reducing the sepal to an unequally pinnate leaf like ordinary rose-leaves. As the sepals rise in the quincuna, the growth becomes weaker, the third bears ; small leaflets only on one side, and the upper or interior sepal terminates
oe a 467, Cercis. iy)
464, Quincunxial 466. Papilionaceous Flower with standard within 468. Cochleate 465.
estivation. eestivation. the wings. zestivation. Rosebud.
ina simple filament. The quincunx estivation may be disturbed by unequal develop- ment of the leaves of the whorl, and this especially occurs in the corolla, owing to the relatively slow or rapid growth of some of the petals. Thus, in the papiliona- ceous corolla (fig. 466), the standard, which represents No. 4 of the quincunx, and ought to be internal, is wholly exterior, because, having developed more rapidly than the other petals, it covers the two wings representing Nos. 1 and 2; this zstivation is said to be papilionaceous (ce. vewillaris). In the St. John’s Bread (Cercis), the standard retains its normal position, and the quincunx is properly formed (fig. 467). In the Snapdragon (fig. 468) and other personate plants, the second petal is interior instead of being exterior, either because it has developed before the others, or because the latter have grown the most rapidly ; this mode of zstivation is called cochleate (w. cochlearis). The calyx has a similar arrangement.
Amongst the varieties of imbricate estivation is that termed convolute! (@. con- volutiva): it occurs when the sepals or petals overlap, so that each completely envelops all the others; as in the calyx of Magnolia, and the corolla of Poppies (fig. 470). Aistivation is alternate (ce. alternativa), when the leaves of the calyx or corolla form two whorls, of which the exterior encloses the interior whilst alternating with it, as in the calyx of the Wallflower, and corolla of Fumetory (fig. 472).
[Mistivation is straight (we. recta), or open (@. aperta), when the parts are so little developed or so distant that they do not meet.—Ep. |
SYMMETRY OF THE FLOWER.
The term symmetry has been differently applied; according to De Candolle, it implies non-geometrical regularity in plants and animals; other botanists distinguish (often obscurely) symmetry from regularity: this we do not admit, but regard
1 The term convolute is often used synonymously with contorted or twisted zstivation.
88 ORGANOGRAPHY AND GLOSSOLOGY.
symmetry and regularity! as synonymous, and as implying a similarity between the leaves of a floral whorl; this relation including :—1, the form; 2, the number; 3, the independence; 4, the relative position of the parts of flowers: we have thus the sym- metry of form, of number, of disjunction, and of position. Symmetry of form is regularity taken in its usual sense; as when portions of a whorl are alike, or when, being different, the one sort alternates with the other, so as to present a symmetrical whole around a common centre; this regularity might be termed rayed symmetry (calyx and corolla of Columbine, fig. 31; Wallflower, fig. 7; and Buttercup). A whorl that is not thus symmetrical is said to be irregular; though its two sides (or halves) may resemble each other, thus being analogous to the longitudinal? symmetry of animals, which is opposed to the rayed symmetry of Zoophytes. ‘The corollas of the Heartsease (fig. 170), Cytisus (figs. 253, 254), Tropwolum (fig. 210), are irregular, but longitudinally symmetrical. The whorl is called regular, even though it forms a depressed spiral ; -but if the floral axis lengthens sensibly, the rayed symmetry dis- appears, and, to describe the symmetry, recourse is had to the comparative length of the spiral; thus the symmetry of the carpels is hemispheric in the Strawberry (fig. 401), conical in the Raspberry (fig. 402), spiked in Adonis (fig. 404). Perfect numerical symmetry occurs when all the whorls consist of the same number of parts, as in Crassula, which has five sepals, petals, stamens and carpels. Disjunctive symmetry occurs when the pieces of each whorl are entirely sepa- rated, and each whorl is entirely free (Columbine, Hellebore). Symmetry of position oceurs when the pieces of each whorl alternate with those of the preceding and succeeding ; and the normal position of the whorls (calyx, corolla, androecium, pistil) is undisturbed (Crassula rubens). Many botanists, regarding regularity as the normal feature in plants, assume it to be the primitive type adopted by Nature; they there- fore look upon a combination of the above-named symmetries as indicating the normal condition of the flower; which should thus consist of four whorls, each composed of the same number of leaves, all equal, free, alternating successively, and arranged in the order of calyx, corolla, androecium and pistil. = Further, such a primitive type, whether real @ 62 ))) or imaginary, may be more or less com- ‘pletely and permanently modified by various single or combined causes, of which the prin- cipal are, — inequality of development, cohe- ee ate sion or symphysis, multiplication, doubling, 400 bt, ina, etl seer, SUPPression and abortion. This hypothe- sis has contributed largely to the progress of organography, by stimulating investigations into the comparative anatomy of floral organs. To ascertain the amount of symmetry a flower displays, its bud must be cut
1 Symmetry in English and American works or equal in number; regularity, that the parts of a implies that the parts of successive whorls are isometric whorl are equal and similar.—Ep, 2 Better called Ailateral—En.
SYMMETRY OF THE FLOWER. 89
through horizontally, when all the whorls will appear projected on the same plane; and the relative positions of the organs thus displayed is termed a diagram (fig. 469). Inequality of development necessarily interferes with symmetry of form (corolla of Heartsease, fig. 170 ; Cytisus, figs. 253, 254; Tropwolum, fig. 210) ; this inequality is frequently caused by the cohesion of parts, as in the bilabiate monosepalous calyx of Lamium (fig. 208), in the bilabiate corolla of Snapdragon (fig. 285), of Linaria (fig. 286), Lamium (figs. 278, 279), in the monadelphous andrecium of Mallow (fig. 810), diadelphous of Lotus (fig. 312), didynamous of Snapdragon (fig. 305), tetradynamous of Wallflower (fig. 306); in the ovary of Snapdragon, the pistil of Orchis, &c.—irregularities which are usually accompanied with nectariferous glands (Heartsease, Wallflower, Centranthus, Honeysuckle, Snapdragon, Linaria, &c.). In Linaria (fig. 286) the calyx is monosepalous with five unequal divisions, the corolla is monopetalous with two unequal lips, of which the upper represents two petals, and the lower three, of which the centre one is prolonged below into a subulate spur; there are four stamens, of which the two longest are situated between the central and the two lateral petals of the lower lip; the two others, which are shorter, are opposite the fissures which separate the two lips; at the base of the upper lip a filament represents the fifth stamen. In certain circumstances all the petals of Linaria are developed like the centre one of the lower lip; the whorl is then perfectly regular, and presents a corolla with five lobes, and five equal spurs between them (fig. 469 bis). At the same time, the filament at the base of the upper lip develops into a stamen like the four others, which latter, usually unequal, become precisely alike, so that the flower is furnished with five symmetrical stamens : to this metamorphosis the name of Peloria has been given, which, according to the theory adverted to, would be regarded as a reversion to the normal state of the plant. Violets are also sometimes regular; sometimes presenting two opposite spurred petals, or three, or even five such; when the symmetry of form is esta- blished in the three first whorls.
Cohesion or symphysis, whether congenital or the result of growth, destroys the symmetry of disjunction by effecting either the cohesion of the leaves of the same whorl, or the cohesion! of one whorl with another; as in monosepalous calyces, monopetalous corollas, monadelphous, diadelphous and polyadelphous stamens, and compound ovaries ; also in flowers with inferior ovaries (Myrtle, fig. 381; Saaitfrage, fig. 382), and with monopetalous staminiferous corollas (Belladonna, fig. 294); in calycifloral (Peach, fig. 868) and gynandrous flowers (Orchis, fig. 188; Aristolochia, fig. 318).
Cohesion also masks numerical symmetry, by causing a compound organ to appear simple, as in the monosepalous calyx, the monopetalous corolla, the com- pound ovary, &c.; and it destroys the symmetry of position, as when the carpels are enclosed in the receptacular tube (Quince, fig. 215), or in causing the andrceecium to appear above the level of the pistil (Orchis, fig. 188; Aristolochia, fig. 318).
Multiplication consists in the repetition of the same whorl; thus, Berberis has
1In English works, the term cohesion is con- same whorl; adhesion, to the union of the organs of fined to the union of two or more organs of the different whorls.—Eb.
90 ORGANOGRAPHY AND GLOSSOLOGY.
three whorls of three sepals, two whorls of three petals, and two whorls of three stamens. The Poppy (fig. 470) has two whorls of two petals, and many whorls, each
g0Gue
&
473, Geranium. 470. Poppy. 471. Columbine. 472, Fumitory. Flower (mag.), without Diagram. Diagram. Diagram. calyx and corolla,
composed of two stamens. The Columbine (fig. 471) has ten whorls of five stamens and two whorls of five scales. The Fumitory (fig. 472) has two whorls of two petals, and two whorls of two stamens, of which the outer are normal two-celled stamens, and the inner stamens are divided into four, each one-celled (equal to two complete stamens). Lythrum has two whorls of six sepals, coherent and adherent. Datura fastuosa has two or three monopetalous corollas, one inside the other.
Deduplication or chorisis occurs when two or more organs take the place of one. This affects not only numerical symmetry, but symmetry of position ; in which respect it differs from multiplication, when the whorls preserve their relative positions. De- duplication is parallel, when the organ is doubled from without inwards, and when the supernumerary piece is opposite to that from which it proceeds; it is collateral, when the supernumerary piece occurs by the side of the organ from which it proceeds, maintaining the same relative position on the receptacle; a parallel deduplication may double or treble the whorl, a collateral deduplication can only increase the number of parts in that whorl, which still continues simple. In the case of parallel dedu- plication, the supernumerary pieces are usually altered, and rather resemble those of the whorl which normally succeeds them, than those of the whorl to which they belong. In Lychnis (figs. 239, 240) and other Caryophyllee, the petals give off a fringed petaloid layer, which coheres with the claw, and is free only where the claw meets the limb; in Sedum (fig. 476) the five petals produce a whorl of five stamens shorter than the five which alternate with them, and the normal and supernumerary andreecia are so close that their bases cohere. In Geraniwm (fig. 473), the five petals produce by deduplication five stamens shorter than and outside the others, but the five larger bear at their outer bases five nectaries, which re-establish the alternation disturbed by the five supernumerary stamens (fig. 474); in Hrodium (fig. 475) the same arrangement exists, except that the extra stamens have no anthers; in Sedwm (fig. 476) the stamens opposite to the petals are a deduplication of the latter; in Flax (fig. 477), the supernumerary stamens are reduced to sessile membranous teeth; in Mignonette (fig. 478), the petals with a fringed top
SYMMETRY OF THE FLOWER. 91
bear within a small concave plate, which is a deduplication of the petal. The petals of Ranunculus (fig. 237) bear at their inner base a small scale, parallel to the claw,
474, Geranium. 475. Erodium. 476. Sedum, 477, Flax. Diagram. Flower (mag.), without cerolla. Flower. Andreecium and pistil (mag.).
and forming with it a nectariferous cavity; the bilabiate petals of Helleborus are formed of two nearly equal plates, and may be regarded as originating by dedupli- cation in a parallel direction. The petaloid lamine of these plants must not be confounded with the different protuberances on the corolla of Comfrey (fig. 269), and other Boraginew, nor with the sort of hairy palate on the lower lip of Snapdragon (fig. 285) and Linaria (fig. 286); which are not the result of deduplication, but are derived from the substance of the petal. Deduplications are chiefly confined to the corolla and andreecium ; they rarely occur in the pistil; in Sedum (fig. 455) there is externally at the base of each carpel a little green glandular scale, parallel to the carpel, and which might be looked upon as a deduplication of this. Deduplications are not always a proof of superfluous vital action ; they may arise from a misdirection of vegetative force; in fact, when one whorl is doubled, the succeeding one is either weakened, modified, or suppressed, as in the Primrose, Pim- pernel (fig. 479), and other Primulacee, which have only five stamens, and these opposite to the petals, thus not forming a normally whorled andreecium, but being referable to a parallel deduplication of the petals; they thus replace the normal andreecium, which however sometimes appears, not as stamens, but as
479. Pimpernel. 480. Samolus. 481, Vine. 478. Mignonette. Siamen Portion of corolla and 482, Rocket. Young flower Corolla (mag.). and petal (mag.). andreecium (mag.). Andreecium. (mag.).
(fig. 481), the five normal stamens are replaced by five nectaries, but fertilization is
secured by five stamens opposite to the petals. Mollateral deduplication is less frequent than parallel ; in the Rocket (fig. 482) and
92 ORGANOGRAPHY AND GLOSSOLOGY.
“
other Cruciferw, the four stamens arranged in pairs alongside the pistil represent two doubled; the filaments of each pair are indeed often connected half-way up, or throughout their length. In the Orange (fig. 483), the andrcecium consists of a single whorl of thirty stamens, whose filaments cohere in bundles of four, five, or six; in St. John’s Wort (fig. 484), the stamens form three or five bundles, of which each may be considered as a doubled stamen; and so in Castor-oil (fig. 315), the stamens of which form branched bundles. Each filament of the Laurel (fig. 485) bears on each side of its base a shortly stipitate gland, which firmly coheres to it, and is sometimes developed into a true stamen. This shows that the stamen of the Laurel with its two glands represents a stamen multiplied into three, of which the two lateral are rudimentary. In many Garlics (fig. 320) the filaments are dilated, and terminated by three teeth, of which the central only bears an anther ; in Pancratium this dilatation is enormous; the lateral lobes of each filament cohere with the neighbouring filaments, and form with them a fringed tube; in Narcissus (fig. 486) this tube is still more remarkable, and assignable to the same origin. Many plants present the case both of multiplication and deduplication ; the flower of Butomus (fig. 487) has three sepals, three petals, six stamens in pairs opposite to the
484, St. John's Wort. Bundle of stamens,
Portion of antieeotnm, Blamen (usa): Digan i re tr a
sepals, three other stamens within the six preceding, also opposite the petals, and six carpels in two series: here we have a multiplication of the andrcecium and pistil, and besides this a collateral deduplication of the first whorl of the andrcecium. When tlie stamens are twice and thrice as many as the petals, and by their extreme closeness seem to form but a single whorl, it may be difficult to decide whether this is a case of collateral deduplication of the andreecium, or of multiplication, or of a dedupli- cation of the corolla added to the normal andrecium. This difficulty is increased when the stamens all cohere. If the stamens are placed exactly on a level, they may be formed by a collateral deduplication (Orange, fig. 483) ; if some are a little within or without the others, which is easily distinguishable, in spite of coherence, then it is a case either of multiplication or of parallel deduplication. It is a case of. multiplication when the outer stamens alternate with the petals (Berberis), but of parallel deduplication when they are opposite to the petals (Geranium, fig. 473).
SYMMETRY OF THE FLOWER. 93
Arrests and suppressions are due to failures of development, and affect more than all other causes the symmetry of the flower. Arrest is the condition of an organ the growth of which has stopped, so that it is reduced to a sort of stump, sometimes glandular; suppression implies that an organ has never even been developed. The outer whorls are more seldom arrested or suppressed than the andrcecium and espe- cially the pistil, which occupies but a narrow area of the receptacle. The suppression or arrest of one or more pieces of a whorl affects the symmetry of number, position and form. For example, Berberis, whose calyx, corolla and andreecium are in threes or multiples of three, has for pistil a single carpel; the Pink (fig. 488), whose other whorls are quinary, has but two carpels; the Heartsease three (fig. 489); in the Bitter Vetch (fig. 490) and other Papilion- acee, the two first whorls are quinary, the third decennary,
488, Pink. 489. Heartsease. 490. Vetch, 492, Scrophu Diagram. Diagram. Diagram. fae ah
whilst the pistil is mono-carpellary ; it is the same with the pistil of the Plum and Peach. The Snapdragon (fig. 491), of which the calyx and corolla are quinary, has (owing to arrest) four stamens, and two carpels due to suppression.
In Scrophularia, with the same arrangement, the fifth stamen is represented by a petaloid scale (fig. 492). The Periwinkle and other Apocynew, as well as many monopetalous families, have five sepals, five petals, five stamens, and two carpels; Polygala (fig. 498) has five sepals, three petals (sometimes five, alternating with the sepals), eight half anthers (equivalent to four stamens), and two carpels. Umbel- lifere (fig. 494) have five sepals, five petals, five stamens and two carpels. The Cornflower, Dandelion, Chrysanthemum and other Composite have quinary corollas and andreecia and a single carpel; in most, the calyx degenerates into a pappus, though in some (Asteriscus, Hymenoxys) it presents five scales. In most Cucurbitacew (Melon, Pumpkin, Cucumber) the calyx and corolla are quinary and the stamens are reduced to two and a half. ‘ In apetalous, moncecious, and dicecious flowers, an entire whorl is suppressed or arrested (Lychnis, Sagina, Chenopodium, fig. 189); some-
Diagram.
times several whorls are wy absent, as in the Ne ettle and 493. Polygala. 494, Coriander. * 495. Mulberry. Mulberry (fig. 495), which mae Diagram. 2 fiower (mag.).
present only a calyx with an androecium, or a pistil. Sometimes several whorls are suppressed, together with one or more pieces of the remaining whorl ; the male flower
94 ORGANOGRAPHY AND GLOSSOLOGY.
of Euphorbia (fig. 333) consists of one whorl, reduced to one stamen; and the female flower (fig. 406) of one whorl of three carpels; the flowers of Arum (figs. 196, 197, 198) consist of a solitary stamen or carpel. Seeds, like the floral whorls, are subject to suppression and arrest; in Geranium (fig. 474) the five carpels are two-ovuled, and but single-seeded ; the Oak (fig. 400) has three carpels forming three two-ovuled cells; the septa become speedily absorbed through the rapid growth of one of the ovules, and the ripe fruit is one-celled and one-seeded. The. Horse-chestnut presents a similar arrest. In the Cornflower and other Composite, in Wheat and other Graminee, the ovule is solitary from the first; at least, a second has never been discovered ; thus offering a case of suppres- sion and not arrest.
The causes which disguise or disturb symmetry in any one flower are not always isolated. In Larkspur we have unequal develop- ment and symphysis in the calyx and corolla, multiplication in the andreecium, and swppression in the pistil; in Asclepias (fig. 496) symphysis in all its whorls, multiplication in its corolla, dedu-
496. Asclepias, plication in the second whorl of the corolla, and suppression in the:
mts). pistil. Mignonette is an example of wnequal development in its calyx,
corolla and andrecium; of symphysis in its pistil, of parallel deduplication in its corolla, of collateral deduplication in its andreecium, and of suppression in its pistil.
THE FRUIT.
The fruit (fructus) is the fertilized and ripe pistil, that is, a pistil enclosing seeds capable of reproducing the plant. It may be accompanied by accessory organs, which are considered as forming an integral part of it, and to which we shall return.
The fruit is apocarpows—1, when its carpels are separate from each other (Columbine, fig. 497; Ranunculus, fig. 524; Bramble, fig. 521; Rose, fig. 525), when each carpel is considered to be a fruit ; 2, when the pistil is formed of a single carpel (Pea, Bladder Senna, fig. 498 ; Apricot, fig. 499 ; Wheat). It is syncar- pous, when its carpels are consolidated into a single body (Tulip, fig. 389; Iris, Campanula, fig. 390; Poppy, fig. 888; Heartseuse, fig. 500).
497. Columbine. 500. Heartsease. Fruit. 498. Bladder Senna. Fruit. 499, Apricot. Open flower, Ripe pistil.
According as each free carpel, or each cell of a syncarpous fruit, or each
THE FRUIT. 95
o
unilocular composite ovary contains one, few, or many seeds, this carpel, cell, or ovary is said to be monospermous (monosperma), oligospermous (oligosperma), or many-seeded (polysperma). The ripe ovary is called a pericurp (pericarpiwm); we have already described the three layers of which it is composed (figs. 15, 16), epicarp, endocarp, and mesocarp or sarcocarp. ;
Changes caused by Maturation.—In ripening, the fruit undergoes changes, some of which have been already mentioned: it may be dry, and then, according to its consistency, it is said to be membranous, corky, coriaceous, woody, bony; the latter quality is found in the Filbert (fig. 238) ; sometimes it becomes fleshy through the abundant pulp of the seed;' in Belladonna (fig. 567) the mesocarp is succulent; in the Orange os 568) the pulp consists of long
501. Gooseberry. 503. Cneorum. 504. ‘Tribulus. 502. Cassia.
‘ruit Fruit cut Fruit cut Portion of open 505, Radish.. cut vertically. vertically (mag.). vertically (mag.). fruit. Flower cut vertically.
spindle-shaped cells, fixed to the endocarp by one of their extremities, and free at the other; in the Tomato it is the placenta, in the Gooseberry (fig. 501) and the Pomegranate it is the testa itself of the seed which is pulpy.
In fruits with a succulent mesocarp, as Plum, Cherry, Peach, Apricot, Walnut, &c., the endocarp thickens at the expense of a portion of the mesocarp (figs. 16, 520), becomes bony, and forms the stone (putamen). The septa sometimes disappear in the pericarp; as in Lychnis (fig. 398) and other Caryophyllacee, where the rapid growth of the walls of the ovary breaks and effaces them; in the Oak (fig. 400), where one ovule stifles the other five, and destroys the three septa; in the Ash (fig. 561), where one of the two cells contains a seed, while the other is reduced to an almost imperceptible cavity by the destruction of the septum. Sometimes trans- verse septa are developed in the ripening ovary; these are horizontal expansions of the endocarp and mesocarp, which sometimes become woody (Cassia, fig. 502). In Oneorwm (fig. 503) and Tribulus (fig. 504), the endocarp and mesocarp are gradually intruded from the inner wall of the ovary, so as to form oblique septa, which at maturity divide the cavity into small superimposed cells. The membranous transverse septa of the cells of the Radish pod (fig. 505), Raphanistrum, and some other Cruci- fere, are longitudinal septa which the growth of ‘the seeds has driven to right and left by the resistance of the endocarp; in this case, the fruit dehisces transversely, each segment containing one seed.
Suture—The ventral suture (sutura ventralis) is the line indicated by the
1 The pulp rarely contributes to the formation by tempting birds, &c., and -it is often an aid to the of the seed; it aids in the- dispersion of fruits germination of the seed.—Ep.
96 ORGANOGRAPHY AND GLOSSOLOGY.
cohering edges of a carpellary leaf, and which faces the axis of the flower; what is (somewhat improperly) called the dorsal suture (s. dorsalis) is nothing but the median nerve of the carpel, which consequently faces the periphery of the flower. This nerve may be masked by the parenchyma developed from the carpel, as in the Peach; it is usually indicated either by a rib (Columbine) or furrow (Astragalus). The ventral suture may also be indicated by a rib (Pea) or furrow (Peach). In a many- celled ovary, the ventral sutures, occupying the axis of the flower, cannot be seen externally, and each cell is indicated by a dorsal line or rib; besides which, we generally see, on the walls of the compound ovary and between its dorsal furrows, other sutures, named parietal (suture parietales), which indicate the union of two septa, or of two parietal placentas (Mallow, fig. 225). In inferior ovaries, those are not sutures which we perceive on the walls of the fruit, but fibro-vascular bundles, which belong to the calyx-tube according to some, to the receptacular tube according to others (Currant). In this case, the calyx-limb often crowns the fruit, in the form of teeth (Fedia, fig. 216), or bristles (Scabious, fig. 229), or a pappus (Dandelion, fig. 222), or a crown (Pomegranate, Medlar).
Accessory Organs.—The style sometimes remains upon the ovary, and grows with the pericarp as it matures; it forms a flattened beak in the Radish and Rocket (fig. 506), a feathery tail in Pulsatilla and Clematis. The receptacle, which in some cases adheres to the ovary, necessarily forms a part of the fruit; such is the recep- tacular tube which encloses the carpels in Apples, Pears, Quinces, Medlars, White- beam, Azarole, Haws, &c.; such is also the receptacle of the Strawberry (fig. 507), which, though almost dry at first, gradually enlarges, becomes fleshy, and encloses the ovaries in its crimson parenchyma; itis not then the pistil alone, but the enlarged receptacle which is prized in the strawberry, and which is usually regarded as the fruit ; the carpels of the strawberry are insipid, and crack under the teeth, and the little black styles appear as dry deciduous threads. In the Fig (fig. 158), a fleshy receptacle encloses innumerable minute flowers, the lower female, the upper male.
Exuvie.—The name exuvie (induvic) has been given to the per- | sistent withered remains ‘{,y of the calyx or corolla, or sometimes of the andreecium, which per- sist around the fruit but do not adhere to 506. Rocket. 507. Beeybentye 509, Rose.” it; in Campanula (fi 3 508. Winter Cherry.
coi oo ea 544) the meer ee eof hall the a and persists on the calyx; in the Marvel of Peru the base of the petaloid perianth envelops the ovary, and resembles one of the integuments of the seed; in the Winter Cherry (fig. 508) the whole calyx persists, enlarging enormously, and enclosing the ovary in an inflated coloured bladder. In the Rose (fig. 509), the
THE FRUIT. 97
calyx-limb dries and decays, but the receptacular tube persists and becomes fleshy. In the ripe Mulberry (fig. 571), the female flowers of which form a dense spike, the four sepals are succulent, and enclose the pistil; they may thus themselves be regarded as belonging to the fruit. Involucres, which we have described in the paragraph on bracts, usually persist around the fruit and grow with it; such is the case with the involucres of Composite, the cups of the Acorn (fig. 232), of the Nut (fig. 233), and of the Chestnut (fig. 234).
Dehiscence.—Dehiscence is the act by-which the ripe pericarp opens to let the seeds escape. Fruits which thus burst spontaneously are called dehiscent (dehiscens : Tulip, Iris, fig. 531); the term indehiscent (indehiscens) is applied to—1, fleshy fruits which do not open, but decay, and thus free the seeds (Apple, figs. 448, 449; Peach, fig. 519; Melon, Pumpkin) ; 2, dry fruits, whose pericarp is pierced by the embryo in germination (Wheat, Buckwheat, Oat, fig. 526; Anemone, fig. 523).
Valves (valve, valvule) are the pieces into which the pistil separates when ripe, to allow the seeds to escape; according to the number of these, the fruit is said to be univalved, bivalved, &c. (wnivalvis, bivalvis, &e.); sometimes the separation is incomplete, the valves only opening to a half or a quarter of their length, or at the top only. Apocarpous fruits’ dehisce by the ventral suture (Columbine, fig. 497 ; Larkspur, fig. 512; Caltha, fig. 511), or by the dorsal nerve (Magnolia), or by both at once (Pea, fig. 516, and other Leguminose) ; in the latter case, there are two valves to one carpel.
The dehiscence of plurilocular syncarpous fruits is septicidal (d. septicida) when the septa split into two parallel plates, and the united carpels separate (St. John’s Wort, fig. 527; Colchicum, fig. 529; Mullein, Scrophularia, fig. 528); each valve then represents a carpel. The placentas may fall away with the valves, or form a solid central column (Salicaria, fig. 530). In all cases, the edges of the valves are said to be inflexed. The dehiscence of plurilocular syncarpous fruits is loculicidal (d. locu- licida) when it takes place by the dorsal suture; this results from the septa being more firmly united than the median fibro-vascular bundles of the carpels; each valve then represents the halves of two carpels, and the valves are described as sep- tiferous in the middle (v. medio-septifere). Sometimes the placentas are continued along the septa (Lily, Iris, fig. 581), at others they remain consolidated into a central column ; sometimes, again, the placentas may retain a portion or the whole of each septum, and the central column then presents as many wings or plates as there were septa in the ovary before its dehiscence (Rhododendron, Datura, fig. 582) ; this variety of loculicidal dehiscence is called septifragal.
The same fruit may be both septicidal and loculicidal; thus, in Foxglove, which is two-carpellary, the septa first separate, then the dorsal nerve of each carpel splits, and each of the four resulting valves represents half a carpel.
Syncarpous fruits with parietal placentas usually dehisce by placental sutures, when each valve represents a carpel, and has placentiferous margins (val. marginibus placentifere, Gentian, fig. 533),—or by the dorsal sutures, when each valve represents the halves of two contiguous carpels, and is placentiferous in the middle (v. medio-
‘placentifere, Heartsease, fig. 5384; Willow, fig. 535),—or by the separation of the valves, H
98 ORGANOGRAPHY AND GLOSSOLOGY.
which leave the placentas in their places (Wallflower, fig. 547; Chelidoniwm, fig. 546).
In some syncarpous fruits, the dehiscence is by valvules or teeth, variously placed, which, by diverging or ascending, form openings for the seeds to escape (Primrose, Lychnis, fig. 542; Snapdragon, fig. 545; Harebell, fig. 544; Poppy, fig. 543). Dehiscence is transverse (d. transversalis) when a compound ovary is halved transversely (Pim- pernel, fic. 537; Henbane, fig. 539; Purslane, fig. 588; Plantain) ;— as also when apocarpous fruits break up transversely into one-
510, Linaria. seeded segments (Coronilla, Sainfoin, fig. 518). Dehiscence is trre-
a gular (d. ruptilis) in fruits with resisting septa and dorsal sutures, but uniformly thin walls; thus, the pericarp of some Linarias (fig. 510) splits into longitudinal ribbons; the fruit of Momordica, Wild Cucumber, &c., rupture thus elastically.
Classification of Fruits—Many authors have attempted this; but their efforts, though resulting in many valuable scientific observations, have sometimes given rise to a very obscure botanical terminology. Linnus admitted five sorts of fruit; Gaertner, thirteen; Mirbel, twenty-one; Desvaux, forty-five; Richard, twenty-four ; Dumortier, thirty-three; Lindley, thirty-six. The following classification, adapted from these several authors, appears to us the simplest and easiest of application ; it includes most of the modifications of form observable in the fruits of phseenogamous plants.
Apocarpous Fruits——1. The follicle (folliculus) is dry, dehiscent, many-seeded,
511. Caltha.
518, Sainfoin. Fruit.
NS
512. 515. Trollius, 517. Lucerne. Larkspur. Fruit. Fruit. 516. Pea, Fruit.
and opens by its ventral suture (Caltha, fig. 511; Larkspur, fig. 512; Peony, fig. 518), or very rarely by the dorsal only (Magnolia). Follicles are rarely solitary, but almost
THE FRUIT. 99
always form a whorl (Columbine, fig. 497; Peony, fig. 513; Caltha, fig. 511), or head (Trollius, fig. 515).—2. The legume (legumen) is a follicle opening into two valves by
520. Cherry. 521. Bramble. 522, Arum. Fruit cut vertically. Fruit. Fruit opened (mag.).
526. Oat. Fruit (mag.). 0, ovary ; 523. Wood Anemone. 524. Ranunculus. v, testa ; 519. Peach. Whole achene and 523 bis. Cornflower. Achenes R, G, C, embryo ; Fruit cut vertically. achene cut vertically. Fruit (mag.). in a head, A, albumen,
its dorsal and ventral sutures (Pea, fig. 516). Some Leyuminose have spirally twisted fruits (Lucerne, fig. 517); of others the fruit is indehiscent and one-seeded, hence a true achene (Trefowl); of others it is a lomentwm, i.e. the legume is contracted at intervals into many cells by transverse septa; when ripe, the fruit separates through the septa of the cells into one-seeded joints (Coronilla, Sainfoin, fig. 518); other legumes are vertically more or less perfectly two-celled, by the in- flexion of the dorsal (Astragalus, fig. 391), or ventral suture (Oxytropis). —3. The drupe (drupa) is indehiscent, usually one-seeded, with a fleshy mesocarp, and stony or bony endocarp (Peach, fig. 519; Cherry, fig. 520; Apricot, Plum, Almond, Walnut). Acim are the small drupes forming the fruit of the Raspberry and Bramble, &c. (fig. 521).—4. The simple berry only differs from the compound berry by originating in a solitary carpel (Berberis, Arum, fig. 522).—5. The achene (acheniwm) is dry, indehiscent, with a single free seed (not adhering to the
525. Rose.
pericarp); it is solitary in the Cornflower (fig. 523 bis) and Dandelion ; Be
cut vertically.
agglomerated in the Ranunculus (fig. 524), Anemone (fig. 523), Rose, (fig. 525), and Strawberry (fig. 401). The wtricle (utriculus) is an achene with a very thin and almost membranous pericarp (Scabious, Amaranth, Statice).—6. The caryopsis (caryopsis) is dry, indehiscent, with a single seed adhering to the pericarp (Wheat, Maize, Oat, fig. 526).
Syncarpous Fruits—7. The capsule (capsula) is dry, one- or many-celled, and dehiscent; it is plurilocular and septicidal in St. John’s Wort (fig. 527), Scrophularia (fig. 528), Mullein, Colchicum (fig. 529), Salicaria (fig. 530); locwlicidal in Lilac, Lily, Tris (fig. 581); septifragal in Datura (fig. 532), septicidal and loculicidal in Digitalis and Linum catharticum. ~ The valves of the unilocular capsule are placentiferous at the edges in Gentian (fig. 533) ; placentiferous at the middle in Heartsease (fig. 534) and Willow (fig. 535). The capsule of Orchis (fig. 536) opens into three valves
H2
100 ORGANOGRAPHY AND GLOSSOLOGY.
placentiferous at the middle, and the median nerves of the three carpels, united by their bases and tops, and crowned by the dry floral envelopes, persist after the valves fall away. In the circwmsciss capsule g (pyxidium, c. circumscissa), the dehiscence is transverse (Plantain, Pimpernel, fig. 537; Purs-
SM SBS,
527, 528, Scrophularia, 530. Salicaria. St. John’s Wort. Fruit. bruit (mag.), 531. Iris. Fruit. 536. Orchis. Fruit.
lane, fig. 588; Henbane, fig. 539). In Mignonette (fig. 540), the capsule opens by the separation of the three sessile connivent stigmatiferous lobes, without dividing into
533. Gentian. 534, Heartsease. 545. Willow. Fruit. Fruit. Fruit (mag.).
: 529. Colchicum. 537. Pimpernel, 5388. Purslane. 539. Henbane. 532, Datura. Fruit. Fruit. Fruit (mag.). Fruit (mag.). Fruit.
teeth or valves, and leaves an opening between them. In the Primrose, the capsule is five-valved at the top, by the fission of the dorsal nerves of the carpels. In the Pink (fig. 541), both the dorsal nerves and placental sutures split. In Lychnis (fig. 542), the capsule is similarly incompletely ten-valved. In the Poppy (fig. 548), the capsule opens by small tooth-like valves between the septa, below the disk formed by the style and stigmatic rays. In the Harebell (fig. 544), the capsule opens by five small valves at the base of the receptacular tube; these openings are formed by the lower portions of the septa separating from the central axis, and carrying up with them a portion of the pericarp, in the shape of a little open door. In other species of Campanula the opening occurs at the upper part of the receptacular tube, where the edge of the septum is thickened and forms
THE FRUIT. 101
a border with the concavity outside; the bottom of this border rolls over the concavity, and ruptures the wall of the ovary, forming between each sepal a little round protuberance, and the seeds escape , ‘ by pores which are on a level with their placentas. In the Snapdragon (fig. 545),
540, Mignonette. 542, Lychnis. 545, Snapdragon. 541. Pink. 543. Poppy. 544, Harebell. Fruit. Fruit. Fruit. Fruit, Fruit. Fruit.
the upper carpel, that next the axis, opens near the persistent style by small free valves; the lower carpel, which is gibbous below, opens by two similar collateral valves, also near the style. The entire fruit, when seen in front, resembles a monkey’s face, the style being the nose, the hole of the upper carpel the mouth, the two other holes the eyes, and the persistent calyx a head-dress.
The siliqua (siliqua) is a capsule with two carpels; it is properly one-celled (Chelidonium, fig. 546), but usually
546. 547. 548, ; ; : Chelidonium Wallflower. Whitlow-grass. 549. Cochlearia. 550. Thiaspi. 551. Bunias, 552, Bunias. Fruit. Fruit. Fruit (mag.). Fruit. Fruit (mag.). Fruit. Fruit, open.
two-celled by a spurious membranous septum, and opens from bottom to top by two valves, the seed-bearing parietal placentas persisting (Wallflower, fig. 547). The silicule (silicwla) is a siliqua of which the length does not much exceed the breadth (Whitlow-grass, fig. 548; Cochlearia, fig. 549; Thlaspi, fig. 550). In some cases the siliqua is lomentaceous, separating transversely into one-seeded joints (Radish). In the Bunias (figs. 551, 552), each of the two cells of the silicule is two- seeded and two-celled, by a longitudinal septum. In Orambe (fig. 553), the silicule is compressed, and 5.5 Gombe.
A 554. Myagrum. originally consists of two unequal one-seeded cells, but Fruit, open. Fruit, open.
whilst the seed of the upper cell becomes developed, that of the lower cell is arrested, its funicle being strangled in the septum; and the result is a one-seeded
102 ORGANOGRAPHY AND GLOSSOLOGY.
indehiscent fruit. In Myagrum perfoliatum (fig. 554), the silicule contains only one seed, which occupies its lower halt, and pushes up the septum; the two upper cells are empty. In plurilocular capsules, the name cose? (cocct) has been given to one- or two-seeded carpels, which separate (often elastically), and carry the seeds with them, but
555. Geranium. 556. Fraxinella. 657, Aithusa, 558. Bugle. 639, Cerinthe, Fruit (mag.). Fruit. Fruit. Fruit (mag.). Fruit.
usually leave the placentas attached to a central column (Creorum, Fraxinella, Euphorbia, Geranium, Mallow). In Huphorbia this central column consists of the placentas, and three double plates, which are portions of the septa, of which the other portions were carried away by the dehiscence of the valves.
In Geranium (fig. 555) the five carpels separate elastically upwards, and roll over upon themselves; the central column consists of the placentas and the edges of the carpellary leaves. In Mallows, the septa of the ten to fifteen carpels split, but the carpels do not wholly separate from the column; a considerable portion of the septa adhering to it. In Frawvinella (fig. 556) the five carpels separate completely, and leave no column.
The fruit of Angelica, Hthusa (fig. 557), and other Umbellifere is a capsule with two one-seeded cells, divided by a narrow septum; its two carpels separate like cocci, and remain suspended at the top to the filiform axis or prolongation of the receptacle. Most botanists consider this fruit to be composed of two achenes; but achenes are apocarpous fruits, and this fruit, being syncarpous, constitutes a true two-celled septicidal capsule, of which the only opening to the carpels is a narrow cleft, pre- viously occupied by a filiform axis. The fruit of the Bugle (fig. 558) is composed of four one-seeded lobes, which separate when ripe, often called achenes and nucules; but the fruit of Borragineee and Labiate is now considered to be formed of two carpels, each distinctly two-lobed, and containing two seeds; this is obvious in Cerinthe (fig. 559). It has been demonstrated that in the very young buds of the
560. Maple. Fruit. Fruit, open.
THE FRUIT. 103
Sage and other Labiatw, there really are only two carpellary leaves, opposite to the two lips of the corolla. Such fruits are not collections of achenes, but syncarpous, the carpels being united below by the dilated style-base (fig. 409); it is a true capsule of two carpels, each of which becomes two-celled, and hence it simulates four distinct carpels. The samara (samara) is a dry, one- to two-seeded fruit, of which the pericarp forms a membranous wing above or round the cell (Maple, Ash, Elm, &c.); these, which are often placed among apocarpous fruits, are evidently composed of two united carpels. In the Maple (fig. 560), the two cells are distinct, and the fruit separates, as in Umbellifere, into two cocci hanging at the top of a filiform axis ; it is therefore a true septicidal capsule, the only opening of the carpels being the narrow slit previously occupied by the axis. In the Ash (fig. 561), the septum is perpendicular to the faces of the ovary, and consequently the two sharp edges answer to the backs of the carpel; after flowering, all the ovules but one are arrested ; the septum is pushed back, one of the cells almost completely disappears, and the other is filled with the seed.
The fruit of the Hlm (fig. 562) is similar; one of the cells is one-ovuled, the other is empty from the first. The nucule (nucula) is an indehiscent capsule, with a bony or coriaceous pericarp, plurilocular when young, but one-celled and one-seeded by arrest (Oak, fig. 232; Filbert, fig. 233; Hornbeam, Beech, Chestnut, fig. 563; Lime, fig. 564). To the same category belong also the fruits of Fedia (figs. 565, 566) and ‘other Valerianew, sometimes for convenience, but not accurately, called achenes.— 8. The berry (bacca) (whether compound or simple) is succulent, indehiscent, and has no stone; it differs from the capsule only in its fleshy consistence, which frequently induces the suppression of the septa, and arrest of some of the seeds (Vine). There are some fruits
565. Fedia. 566. Fedia. Fruit cut ¥ruit ent 562. Elm, 563. Chestnut. 564. Lime. transversely vertically 567. Belladonna, Fruit. Fruit. Fruit. (mag.). (mag.). Fruit.
which may equally be termed a berry or a capsule (Capsicum, Winter Cherry). Among species of the same genus, some are provided with a capsule, others with a berry (Galiwm, Asperula, Campion, Hypericum). The Privet, Nightshade, Belladonna (fig. 567), Vine, have a two-celled berry ; Asparagus and Lily of the Valley, a three-celled berry; Herb Paris, a four- to five-celled berry. Among plants with an inferior ovary, the berry of Sambucus is three-celled, that of the Myrtle four- to five-celled ; Ivy, five-celled ; Coffee, two-celled ; Gooseberry, one-celled, with parietal placentas (fig. 501). The hesperidiwm (hesperidium) is a plurilocular berry, with an aromatic glandular epicarp, a dry and spongy mesocarp, an endocarp covered with
~
104 ORGANOGRAPHY AND GLOSSOLOGY.
small watery cells which spring from the walls of the cavities, and extend to the seeds (Orange, fig. 568). The gourd (pepo) is a berry composed of three to five (rarely one) carpels, united to the receptacular tube, and forming a single cell with very fleshy seed-bearing parietal placentas (Melon, Pumpkin, Sechiwm, Briony). The pome (pomwm, melonida, figs. 569, 570), is a berry composed of many (usually five) cartilaginous carpels (£), forming five cells, and united to the receptacular tube (rT) (Apple,
568, Orange. 570. Apple. 569. Apple. 671. Mulberry. Fruit cut transversely. Fruit cut vertically. Fruit cut transversely. Fruit.
Pear, Quince).—9. The compound drupe (nuculanium) is fleshy, and encloses many stones, which are sometimes connate (Dogwood), sometimes free (Medlar, Beam, Sapotilla).
Aggregate fruits is the name given to fruits that result from the union of several flowers ; these component fruits are included amongst the above-described varieties. In the Honeysuckle, the fruit is formed of two connate, but originally free berries. In the Mulberry (fig. 571), the true fruit consists of a spike or head of small drupes, each enveloped in a succulent calyx. The Fg (fig. 158) is a pyriform body, fleshy, hollow, bracteate at the base, the mouth furnished with little scales, and serving as a common receptacle to the flowers enclosed in its cavity, the males above, the females below. In the Pine-apple (fig. 572), the flowers are spiked and pressed round an axis
573. Pine. Carpel (mag.) bearing two seeds. Ch, chalaza ; 672. Pine-apple. M, micropyle. 574, Pine, Fruit. 575. Cypress. Fruit.
576. Juniper. nuit.
terminating in a tuft of leaves; the ovaries form so many berries, but the calyces, the bracts, and the axis itself become fleshy. The Pine-cone (conus, strobilus) is an aggregate fruit, which has nothing in common with the preceding; the carpels, represented by scales (fig. 573), have neither style nor stigma, and do not
SEED. 105
close to shelter the seeds, but protect them by closely overlapping each other until ripe. They are sometimes woody, when they form either a conical spike (Pine, fig.
574), or a globular head (Cypress, fig. 575); when fleshy and connate, they simulate a drupe (Juniper, fig. 576).
SEED.
The seed (semen) of pheenogams is the ovule when fertilized, ripe, and ready for germination ; it contains the embryo (embryo, plantula, corceulum), which is destined to reproduce the mother-plant. Let us recapitulate the structure of the embryo in the Pea (fig. 577). Itis composed of a caulicle (cauliculus, tT), a radicle (radicula, R), two cotyledons (cotyledones, c), and yy ae a plumule (gemmula, plumula); it is enveloped by a double integument, of which the outer (1), or testa (testa), attached to the hilum (hilus, umbilicus) by the funicle (funiculus, F), which rises from the placenta (placenta, P); and the inner (£), or endopleure,' (endopleuwra) provides a passage for the nourishing juices by the chalaza (chalaza, 4), a are which communicates with the hilum by means ofa cord (4), © H AFP the raphe (raphe). Near the hilum is a small opening (M), “hat ite intazumont and one of the micropyle (micropyle), by which the ovule is fertilized by “71995 the pollen. As a general rule, the radicular end of the embryo answers to the micropyle, and the cotyledonary end to the chalaza; the exceptions to this rule, which are rare, and do not invalidate it, will be specified.
Relative Positions of Seed and Embryo.—It is important to observe that, in the early condition of the ovule, the hilum and chalaza are united; consequently the raphe does not exist, and the micropyle occupies the opposite, or free end of the ovule; also that 1, the base of the fruit (ovary’), is the point by which this is auaeneD to the receptacle, and its top is the point from which the style springs;
. 2, the base of the seed is the point by which it is attached to the futaela or placenta, and which is indicated by the hilum; the top of the seed is the extremity of an imaginary simalight or curved line drawn through the axis of the seed. The axis of the ovary is defined in the same manner. The embryo has also its azis; its base is its radicular, and its top its Bip aTetule: cotyledonary extremity.
Achene cut vertically (mag.) . 5 showing one of the large The top of the seed is obvious
sepals; the ovary terge me Whenever the hilum occupies either
aap ae er a funi’e extremity of the long axis of the seed, 559, Chicory. BG Rie:
ag . N Achene cut vertically paren oa nas, Owe as 18 usually the case ( ettle, fig. aug certiealle (mag.). OV, ovary; »
the-top of Ene Ovary: 578; Sage, fig. 579; Chicory, 580) ; (mag). Gr seed: but sometimes the hilum is placed at the middle of the long axis of the seed
1 Sometimes called tegmen.—Ep. seed in relation to the ovary, where we should say 2 Throughout this section the authors speak of the carpel or frwit.—Ep,
106 ORGANOGRAPHY AND GLOSSOLOGY.
(Lychnis, fig. 587); itis then ventral (h. ventralis), and when the seed is flattened (Madder) it is described as depressed (s. depressum), or peltate (s. peltatwm) if it is convex on one side and concave !
on the other (Lychnis, Stellaria). In these latter cases it is difficult and superfluous to determine the top of the seed, but it is easy and
581. Sedum. 582. Valerian. 583, Plumbago. Flower cut vertically (mag.). Flower cut vertically (mag.). Flower cut vertically (mag.),
important to distinguish the ventral face, i.e. that facing the placenta, and the dorsal or opposite face. The seed is erect (s. erectum) when it is fixed to the bottom of the cavity of the fruit (Netile, fig. 578; Sage, fig. 579). It is ascending (s. ascendens), when, being fixed to a central or parietal placenta, its top is turned towards that of the fruit (Sedum, fig. 581; Apple, fig. 570). The seed is reversed (s. inversum) when its base corresponds to the top of the fruit, whether the placenta is immediately under the style (Valerian, fig. 582), or at the bottom of the ovary, in which case the seed is suspended from an ascending basal funicle (Plumbago, fig. 583). The seed is suspended, pendent (s. pendulum), when it is fixed to a central or parietal placenta, with its top turned towards the base of the fruit (Apricot, Almond, fig. 583 bis). The distinction between reversed and pendulous seeds is often very slight, and these terms are often used indifferently to describe a seed of which the free end faces the bottom of the fruit. The seed is horizontal when fixed to a central or parietal placenta, with its axis at right angles to that of the fruit (Aristolochia, Lily, fig. 584).
ovule may be pendulous and the other ascending (Horse-chestnut, fig. 585); in others with many seeds or ovules, some are ascending, others pendulous, and ‘ale those in the centre horizontal (Colum- ‘Oh bine). All the terms indicating the ae position of the seed are equally applicable \W to that of the ovule.
( In certain two-ovuled ovaries one
584. Lily. 585. Horse-chestnut. M s G Orne eee Pate The radicle is superior (r. supera) 683 bis, Almond. transversely (mag.). vertically (mag.).
when it points to the top of the ovary; it is inferior (r. mfera) when it faces the bottom; thus corresponding to the erect and
SEED. 107
ascending seeds. Thus, the Nettle (fig. 578) has an erect seed and a superior radicle; the axis of the seed is straight, the radicular end being furthest from the cotyledonary, which answers to the hilum. In the Sage (fig. 579) and Chicory (fig. 580), the seed is erect, with an inferior radicle; here the embryo seems to have twisted half round upon itself; the cotyledonary end, which ought to answer to the hilum, being at the opposite extremity, and the radicle nearly occupying its place; this movement has taken place in the cavity of the ovule before fertilization, as we shall presently explain; the result is a long raphe, which runs along one side of the seed, and the chalaza is consequently diametrically opposite to the hilum. The radicle is centri- petal (r. centripeta) when it faces the central axis of the fruit (Lily, fig. 584); centri- fugal (r. centrifuga), when it faces the circumference (Mignonette, fig. 384). The
586. Wallflower. 587. Lychnis. 588. Datura. 589. Marvel of Peru. 591. Plantain. 592. Plantain. Seed cut Seed cut Seed cut Fruit Ventral surface Seed cut vertically (mag.). vertically (mag.). vertically (mag.). cut vertically. of seed (mag.), vertically (mag.).
embryo is antitropal (e. antitropus), when, its axis being straight, the micropyle (and radicle) is furthest from the hilum (Nettle, fig. 578; Ruwmezw, fig. 644); it is homo- tropal (e. homotropus) when, its axis being straight, the micropyle (and radicle) is next the hilum, while the chalaza (and cotyledonary end) is distant from the hilum, and only connected with it by a raphe; then the base of the seed (hilum) and of the embryo (radicle) correspond (whence the term homotropal, Sage, fig. 579; Chicory, fic. 580; Pear, Apricot, Rose, Strawberry, Scabious, Centranthus, Campanula, Hearts- ease, Iris, &c.). The embryo is amphitropal (e. amphitropus) when, its axis being bent, the micropyle and chalaza are both close to the hilum (Wallflower, fig. 586; Lychnis, fig. 587; Datura, fig. 588; Marvel of Peru, fig. 589; Mulberry, fig. 590). The embryo is heterotropal (ec. heterotropus) when, from the unequal growth of the coats, neither extremity of the embryo corresponds to the hilum, and the radicle does not correspond
590. Mulberry. 593. Palm. 594, Asparagus. . 597. 596. Pine. Ovary cut eed Seed cut 595. Spergularia. Colnmbine. Seed. vertically (mag.). cut vertically. vertically (mag.). Seed (mag.). Seed (mag.).
to the micropyle; in this case, the axis of the embryo is sometimes parallel to the plane of the hilum (Pimpernel, Plantain, figs. 591, 592), sometimes oblique to it (Wheat, Chamerops, fig. 593; Asparagus, fig. 594); the radicle is then said to be excentric (r. vaga, excentrica).
108 ORGANOGRAPHY AND GLOSSOLOGY.
Form and Surface of the Seeds.—According to their form, seeds are globular, ovoid, reniform, oblong, cylindric, turbinate, flattened, lenticular, angular, &c.; some are irregular, flat, and rather like grains of sawdust, and are said to be scobiform (s. scobi- ' formia); flattened seeds with thick and projecting edges are said to be margined (s. marginata) (Spergularia, fig. 595), or winged if these margins become broad and membranous (Bignonia, Pine, fig. 596). The surface may be smooth (s. leve, Colum- bine, fig. 597); wrinkled (s. rugoswm, Fennel, fig. 598); striate (s. striatum, Tobacco, fig. 599); ribbed or furrowed (s. costatum, Larkspur, fig. 600) ; reticulate (resembling a sort of network (s. reticulatum, Cress, fig. 601) ; punctate (s. punctatum), i.e. marked with little dots; alveolate (s. alveolatum), i.e. covered with little pits resemblifig
598. Fennel. 599. Tobacco. 600. Larkspur. 601. Cress. 602. Poppy. 603, Stellaria, Seed (mag.). Seed (mag.). Seed (mag.). Seed (mag.). Seed (mag.). Seed (mag.).
honeycomb (Poppy, fig. 602); tubercled (s. tuberculatum), i.e. furnished with small rounded projections (Stellaria, fig. 603); aculeate (s. aculeatwm), i.e. bristling with small points (Snapdragon, fig. 604); glabrous (Flax); hairy (Cotton). Some seeds have a pulpy testa (Gooseberry, fig. 605; Pomegranate); others are covered with oily glands, often arranged in bands (Angelica, fig. 606); sometimes placed in furrows (Juniper, fig. 607).
The hilum, or point by which the seed is attached to the funicle or placenta, forms a depressed or prominent scar; in the middle or towards one side of this scar, is the umbilicus, a very small simple or compound orifice, indicating the passage of the nourishing vessels of the funicle into the seed. The chalaza, or internal hilum,
605. Gooseberry. P 604. Snapdragon. Seed cut 606. Angelica, 607. Juniper. 608. Orange. 609. Orange. Seed (mag.). vertically (mag.). Seed (mag.). Seed (mag.). Seed, open. Whole seed.
forms sometimes a more or less distinct protuberance, sometimes a sort of knob, sometimes a simple blotch (Orange, fig. 608, Almond). The raphe, which maintains the communication between the hilum and chalaza when these are separated during the development of the ovule, appears like a band along one side of the seed; often it branches out in the thickness of the testa (Almond, Orange, fig. 609). The miero- pyle, which in the ovule formed a large gaping opening, remains visible on some seeds (Bean, Kidney-bean, Pea); it disappears in most, but its position is usually indicated by that of the tip of the radicle.
The Proper and Accessory Coats of the Seeds.—Seeds do not always possess a
SEED. 109
distinguishable testa and endopleure; often, when ripe, all the coats merge into one, or one splits up into several layers, and the seed presents three or four coats. The origins of these envelopes will be described under the development of the ovule.
Arils are accessory organs, which mostly develop after fertilization, and cover the seed more or less completely, without adhering to the testa; some are expansions of the funicle, and are specially designated as aril (arillus) (Nymphea, Passiflora, Opuntia, Willow, Yew); others arise from the dilatation of the edges of the micro- pyle, and are called by some authors arillodes or false arils (arillodes).
In the White Water Lily (fig. 610) a swelling (a, a), rising from the funicle (F), gradually spreads over and caps the ovule, and ends by closely enveloping the seed, without adhering to it, leaving scarcely a trace of an opening over the chalaza (Ch.). In Passion-flowers
M.
612. Yew. Young ¢ flower.
612, Yew. @ flower, older,
WZEEE RSS line 1 Wy
TAN Cea ig WS
4 2 610. White Nymphea. _ 614. Yew. 615, 616, 617. 618. Vertical section of the young 611. Willow. Ripe fruit, sunk in European Spindle-tree, showing the successive Seed (mag.). Seed (mag.). its fleshy aril. developments of the arillode.
an annular swelling, with a free membranous torn margin, forms at the shortened end of the funicle, round the hilum; this gradually expands, and ends by en- closing the seed in a loose fleshy bag, with a large opening towards the chalaza. In Willows (fig. 611), the very short thick funicle expands into an erect pencil of hairs, which envelops the seed. In Cactus Opuntia, two concave boat-shaped expansions spring laterally from the funicle, into which the ovule-is pushed, and within which it is developed; this accessory envelope thickens, hardens, and forms a sort of stone, covered with pulp. In the Yew, the female flower (fig. 612) consists of a single ovule, which is at first protected only by the scales of the bud from which it issued, and after fertilization disengages itself from these, when it is completely naked, with a gaping micropyle at its summit. Soon (fig. 613), between the ovule and the scales at its base, a small cup is developed, which gradually swells, becomes red and succulent, and ends by almost entirely covering the seed (fig. 614) ; this cup is nothing but an enormous development of the funicle, which thus furnishes an envelope to the fruit, which had not even the protecting scale of the Pines and Firs (tig. 879). In the Spindle-tree (figs. 615, 616, 617, 618), the successive stages of development of the arillode (a) are easily followed (1, 2, 3, 4); it does not spring from the funicle (f), but from the micropyle, the edges of which dilate by degrees so as to form around the seed a succulent, loose, folded bag, open towards the chalaza.
110 ORGANOGRAPHY AND GLOSSOLOGY.
It must be observed that this arillode, starting from the micropyle, which is very near the hilum, unites at a very early stage with the funicle, of which it appears to be an appendage, but its origin may be recognized in very young ovules. In the Nutmeg, the fleshy and honeycombed envelope of the seed, which forms the aromatic substance called mace, may be looked upon as an expansion of the micropyle. In Euphorbia (fig. 619), the circumference of the micropyle, which formed at first a little swelling, thickens enormously after fertilization, and forms a small fleshy disk, of which the central canal, at first filled with the conducting tissue, becomes by
degrees stopped up. In Polygala (fig. 620), the little three-lobed il | } body at the base of the seed has the same origin as the disk of
Nit
SS
621. Asclepias, 619. Euphorbia. 620, Polygala. 622. 623, Chelidonium, 624 Seed (mag.) Seed crowned by Seed capped by a Heartsease, Seed cut Asarum. with hairy arillode. a fleshy arillode cartilaginous arillode Seed (mag.). vertically (mag.). Seed (mag.). (mag.). (mag.).
Euphorbia, and the micropyle is visible long after fertilization. In Asclepias (fig. 621) the tuft of hairs which crowns the seed is also an arillode proceeding from the micropyle.
The name of strophioles (strophiole, caruncule) has been given to excrescences on the testa which are independent of the funicle or micropyle, as the glandular crest which in Heartsease (fig. 622) and Chelidoniwm (fig. 623) marks the passage of the raphe; the cellular mass which in Asarwm (fig. 624) extends from the hilum to beyond the chalaza, and the tuft of hairs at the chalaza in Epilobiwm (fig. 625). The name aril having been indifferently applied to true arils, arillodes, strophioles, &c., it would be advisable to keep this term as a general name for excrescences of various sorts which appear upon seeds, and to limnit the meaning by an adjective indicating their origin. We should thus have a funicular aril (Willow, Nymphea, Yew); a micropylar aril (Spindle-tree, Euphorbia, Polygala, Asclepias); a raphean aril (Chelidonium, Asarum); a chalazian aril (Hpi- lobinm), &c. A second adjective might denote its membranous, fleshy, hairy, &c. texture.
630. Cuscuta.
rors : 627. Berberis. 628. Walnut. 629, Lime. Embryo coiled
625. Epilobium (mag.). 626. Pine. Seed ent Seed Embryo spread. round its
Chalazian tuft of hairs. ea vertically (mag.). cut vertically, out (mag.). albumen (mag.). mag.).
Embryo or Young Plant.—In most pheenogamic plants the embryo is dicotyledonous,
SEED. 111
whence the name Dicotyledons. Some species (Pines, fig. 626), possess six, nine, and even fifteen whorled cotyledons.
Other phenogamic plants have only one cotyledon; whence the name Mono- cotyledons. The colour of the embryo varies; it is white in most plants, yellow in some Crucifere, blue in Salpiglossis, green in the Spindle-tree and Maples, and pink in Thalia. The cotyledons are generally fleshy, their parenchyma is oily in the Walnut and the Almond, and mealy in the Kidney-bean; they have sometimes dis- tinct nerves (Berberis, fig. 627) 5 they are sessile or petioled, or reduced to a petiole without a limb; this is especially the case in monocotyledons. They are usually entire and equal, but may be lobed (Geranium, Walnut, fig. 628), or palmate (Lime, fig. 629), or very unequal, with the smaller so minute that the plant might be mis- taken for a monocotyledon (Trapa). Those of the Nasturtium and Horse-chestnut. unite as they grow old into a compact inass. In some parasites they entirely disappear, and the embryo is reduced to its axis; as in Cuscuta (fig. 630), whose thread-like stem
632. Bindweed. 633. Wallflower. 634, Rocket. 635. Orange, 637. Almond. 638, Almond. 631. Mallow. Embryo spread Transverse section Transverse section Seed without Doub!e Embryos Embryo (mag.). out (mag.). of seed (mag.). of seed (mag.). its testa. embryo. separated.
is attached to the plants it preys on, by suckers (p. 16, fig. 48); and living on -their juices, it needs no leaves to elaborate sap; and the adult plant, like the embryo, possesses no leaves. Cotyledons are sometimes folded in .
halves, along their median line; or convolute (Mallow, fig. 631) ; , or spiral (Hop); or crumpled (Bindweed, fig. 632); the embryo itself is straight, or curved, or zigzag, or annular, or spiral, or rolled into a ball, &c. Often the radicle is turned up on the cotyledons ; if it is then placed against their commissure it is said to be lateral, and the cotyledons are accumbent (c. accwmbentes, Wallflower, fig. 633) ; if it is on the back of one of the cotyledons, it is said to be dorsal, and the cotyledons are incumbent (c. incumbentes, Rocket, fig. 634).
Some seeds contain several embryos ; the Orange (fig. 635) has often two, three, or four unequal, irregular, and convolute, the cotyledonary .ends of all facing the chalaza, and their radicles facing the micropyle; they all leave the seed at the period of germination (fig. 636). The seed of the Almond frequently pre- sents two superimposed embryos, one of which appears to proceed from the first, like successive internodes (fig. 637) ; they may be eters easily separated (fig. 638), when their respective radicles and testa 5, included cotsle two cotyledons can be plainly seen. tule,
The monocotyledonous embryo is usually cylindri or ovoid; to distinguish the
112 ORGANOGRAPHY AND GLOSSOLOGY.
parts of which it is composed, it must be cut vertically, when it usually discloses an elongated axis with a small protuberance marked with an oblique or vertical fissure ; this protuberance represents the plumule ; the fissure through which the two first leaves will appear marks the separation between the caulicle and cotyledon. Owing to the small size of the parts, it is sometimes difficult to distinguish the cotyledonary from the radicular end; but the latter, which answers to the micropyle, is usually nearer to the integument than the former; this is evident in the seed of Arum (fig. 639). In Oats and other Graminee (fig. 640), the i
seed, if halved longitudinally along the furrow on its inner ‘
face, discloses a very abundant farinaceous parenchyma (a), of which we shall presently speak ; from the base of the seed along its dorsal face rises the embryo (R, G, ¢), of a yellow, semi- transparent colour; within this is a fleshy leaf (c), which extends one-third of the length of the seed; this leaf encloses several others, successively smaller (¢), which enfold each other, and are placed between the largest leaf (c) and the dorsal face of the ovary (0); all rise from
639, Arum. 641. Oat. ” 643, Aconite, 640. Oat. 642, Oat. Seed cut Isolated embryo seen on Seed cut Vertical section of Germinating embryo. vertically (mag.). its outer face (mag.). Vertically (mag.). fruit (mag.), (mag. ). an enlarged neck which narrows towards the base into an obtuse cone; the interior leaf (c) is the cotyledon, the others (@) form the plumule, the conical disk is the caulicle, terminated by the radicular end (R).
If we extract the entire embryo (fig. 641), we perceive the cotyledon, which is large, and hollowed into a sort of spoon-shape, in the middle of which lies the plumule, forming a closed bag ; in the middle of this bag is a very small longitudinal slit, which enlarges later into a sheath, to open a passage for the contained leaves ; below is the caulicle, bearing the cotyledon on its side, and the plumule in its axis; its free end is terminated by rounded protuberances, in which holes will form, whence radicular fibres will emerge at the period of germination, as from so many sheaths (fig. 642, Col.).
Albumen.—Many seeds contain, besides the embryo, a disconnected accessory mass of parenchyma, named albumen (albumen, perispermum), the formation of which will be explained in the chapter on the Ovule. It is destined to nourish the embryo, and exists at an early period in all seeds; if only a portion of it is absorbed by the embryo, the rest hardens, up to the period of germination, and the embryo is said to be albwminous (e. albuminosus) ; if it be absorbed, the embryo is exalbuminous
SEED. 1138
(e. ecalbuminosus). The albumen may be very copious (Aconite, fig. 643), or extremely thin and almost membranous ; in general it is largest when the embryo is smallest, and vice versa. It is said to be farinaceous (a. farinacewm), when its cells are filled with starch (Buckwheat, Barley, Oats, fig. 640; Rumex, fig. 644) ; fleshy (a. carnosum), when its parenchyma, without being farinaceous, is thick and soft (Berberis, fig. 627 ; Heartsease, fig. 645; Nightshade); mucilaginous (a. mucilaginosum), when it is suc- culent and almost liquid; it is then rapidly absorbed, and may almost entirely dis-
644, Rumex. 645. Heartsease. 646. Poppy. 648. Rose Campion. 649. Ivy. Fruit Seed Seed cut 647. Nymphea. Seed Seed cut
cut vertically cut vertically vertically Seed (mag.). cut vertically vertically (mag.). €mag.). (mag.).. (mag.). (mag.).
appear (Bindweed)} ; oleaginous (a. oleaginosum), when, its parenchyma contains a fixed
oil (Poppy, fig. 646}; horny (a. cornewm)}, when its parenchyma thickens and hardens
(Galium, Coffee, Iris); like ivory (a. eburneum), when it has the consistency and
polish of ivory (Phytelephas). In Pepper and Nymphea (fig. 647), &., the seed contains two sorts of albumen ; which will be noticed when treating of the owule.
The embryo is awile, when its direction corresponds with that of the axis of the seed (Heartsease, fig. 645); it is peripherie (e. pert- phericus), when it follows the circumference of the seed, and surrounds the albumen (Rose Campion, fig. 648) ; it is ruminate (a. rumina- tum), when the testa or endopleura forms folds which areprojected in the interior of the seed, and form incomplete septa in the thickness of the albumen, like the folds found in the
650. Kidney-bean. double stomach of ruminating mammals (Ivy,
Seed germinating.
fig. 649).
Germination — Germination is the action by which the embryo grows and throws off its coats, finally supporting itself by draw- ing its nourishment from without.
The free end of the caulicle (fig. 650, rT), terminated by the radicle, usually enlarges the orifice of the micropyle, and. | .
i’ . Orange seed germi. emerges ; soon the entire caulicle throws off its envelopes, with nating. o,. oo ‘the cotyledons (c) and the plumule (¢); the latter lengthens in its turn, and its little leaves expand as it rises; at the same time the radicle develops, and descends into the earth. If the caulicle, which is the first internode I
114 ORGANOGRAPHY AND GLOSSOLOGY.
of the plant, lengthens during germination, the cotyledons are raised, and appear above ground; they are then said to be epigeal (c. epigwi, Kidney-bean, fig. 650; Radish, Lime). When the caulicle is very short, and the plumule (which forms the second internode) rapidly lengthens, the cotyledons remain in the ground, often even within the seed-coats; they are then gaid to be hypogeal (c. hypoget, Spanish Kidney- bean, Oak, Graminew, Orange, fig. 651).
In monocotyledons, the evolution of the radicle presents a remarkable pecu- liarity: it is provided at the base (fig. -642) with a sort of sheath, named the coleorhiza ; this is nothing but an outer cellular layer which, having been unable to accompany the development of the radicle (x), has been pierced by it.
ANATOMY.
In OrnGaNoGRAPHY we have described the fundamental organs which provide for the growth and reproduction of plants; namely, the root, the stem, the leaves, the floral whorls, and the seed; but these are themselves composed of parts which cannot be studied without the aid of the microscope. These parts, the structure of which varies but little in different plants, and which are elementary vegetable tissues, are named elementary organs; and the science which treats of them is called Vegetable Histology, or Vegetable Anatomy.
ELEMENTARY ORGANS.
If we examine microscopically the thinnest possible slice of a stem, root, leaf, or floral organ, it will present many different cavities, some entirely enclosed in walls, others having no proper walls, but being interspaces between the first; taken together, they present the appearance of a fabric or tissue; whence the name vege- table tissue. ‘
The closed cavities present three principal modifications:—1. Cells—Their diameter is [originally] nearly equal every way. 2. Fibres.—These are longer than broad, and their two ends are spindle-shaped. 3. Vessels, or lengthened sacs, the two ends of which cannot be seen at once under the microscope.
Cells are very variable in shape, depending on the manner in which they are arranged. If they are not crowded, they retain their primitive form of spheroids or ovoids (fig. 652); butif the contiguous faces become pressed together in the
poo% Elder. course of their growth, they become poly- hedral, and may be dodecahedrons, or four-sided prisms, either lengthened into columns, or tabular, or cubical. A transverse section of prismatic o A 653. Tlder. 654, Lily. cells presents equal squares, a vertical section of dode- Cellar tissue of the Elongated cahedral cells presents hexagons (fig. 653) like a aie ia ca honeycomb; whence the name of cellular tissue given to these cells collectively. Lastly, the cells may be placed end to end, like superimposed cylinders or barrels (fig. 654). When the cellular tissue (parenchyma) is very compact, there are no interstices 12
116 ANATOMY.
between the surfaces of the cells; but if the tissue is loose, the cells retain their rounded form, and leave larger or smaller intercellular canals (fig. 655). These spaces occur between polyhedral cells when an interposed liquid or gas displaces them; and it may happen (fig. 655) that if a regular pressure is exerted in neigh- bouring spaces, each of which is circumscribed by a small number of cells, the latter may be disjointed, and a portion of their walls pressed inwards; but where there are two contiguous spaces, the pressures from without will counteract each other, and the cells remain coherent; they then take the shape of stars, the contiguous rays forming isthmuses which separate the spaces.
Sometimes the intercellular space is circumscribed by a great many cells; it is then called a lacuna. These lacune do not always result from the displacement of the surrounding cells, but from the destruction of several of them, or the rapid growth of the plant.
In their earliest condition cells are sacs surrounded by a thin homogeneous membrane, which is soft and moist at first, but dries by degrees. Sometimes this membrane constitutes the sole wall of the cell, sometimes it is lined by a second ; but the latter does not form a continuous sac; it is wanting here and there, and only partially lines the outer membrane; the result is that there are thin areas where
655. Bean. 656. Elder. 657. Mistleto. 658. Mistleto. 659. Orchid. Starred cells. Rayed @ells. Rayed and reticulate cell. Annular cell, Spiral cell.
there is but one membrane, and thick areas where there are two. When the inner membrane is deficient only in small spots, these appear as punctures (fig. 652) or short lines (fig. 656) ; when it is absent over considerable irregular areas, the thin places form an irregular network (fig. 657), of which the open parts answer to those where the inner membraie is wanting, and the threads to the parts where it lines the outer membrane. Lastly, when the solution of continuity of the inner membrane is extremely regular, the open spaces are separated by parallel thickened rings (fig. 658), or a thickened spiral which passes from one end of the cell to the other (fig. 659). Cells may either be homogeneous, or punctate, or rayed, or reticulate, or spiral, or annular; and in many cases the same cell passes successively through more than one of these forms. It frequently happens that a third, fourth, or fifth membrane is developed within the second, by which the wall of the cell is corre- spondingly thickened. It has been observed that these successive membranes usually mould themselves upon the second, so that the thin and thick portions of the cell correspond throughout.
' Fibres.—The length of these varies, but most have a very thick wall, formed at first of a single membrane, lined by a succession of others developed within it; and as the cavity of the fibre diminishes more and more with age, the fibre finally appears
ELEMENTARY ORGANS. 117
nearly filled up. The canal which forms its axis is cylindric; but its outer walls, which are pressed against those of the neighbouring fibres, are flattened and pris- matic, as may be seen by a transverse section of fibrous tissue (fig. 660). The fibres, being spindle-shaped at their extremities, cannot be in juxtaposition throughout their length, but the extremities of other fibres are inserted between their free portions, and hermetically close the conical interspaces above and below them (fig. 661). When the successive inner layers completely line the outer layer, as frequently happens, the F&1 cavity of the fibre remains smooth; if the second layer does not com- § pletely line the first, spiral or reticulate thickenings are the result (spiral or reticulate fibre); and dotted or punctate fibre (fig. 661), the most common form of all, is the result of the failure of the i inner layer over minute areas. Vessels are much elongated tubes, the walls of which are never smooth, but present either slender spots or limes, or a close network, or rings, or spiral lines; they are cylindric, and constricted at intervals (fig. 668). The contractions are circular and hori- e zontal and close set, or oblique and distant. If _ 660, onina regia. 661. Clematis, the vessel be boiled in dilute nitric acid, it breaks “""*°™ "msvenev-— Punctato bre, up at the strie. Where the constrictions occur, membranous folds often project as lings or perforated diaphragms into the interior; whence it has been concluded that the vessel is formed partly of cells, partly of fibres joined end to end, of which the ends, which at first formed septa, have gradually become obliterated or per- forated. The vessels, like the cells and fibres, are named, according to the appearance of their walls, punctate, striate,
\
| A (QQ
CC CA
——4 reticulate, annular, spiral. The spiral vessels, or trachee (fig. = 662), are membranous tubes, uninterruptedly traversed = within by a pearly white spiral thread; this thread is
(
neither tubular nor channelled, but cylindric, flattened. (fig. 663), or a four-sided prism. The trachee being spindle-shaped at each end (fig. 662), are regarded as elongated fibres. Nothing is easier than to examine these trachez: if young shoots of Rose or Elder be gently broken, there will be seen by the naked eye between the ruptured
662. Melon, Surfaces a spiral thread, lengthening and shortening like
Trachee. 4, piece of elastic. The outer membrane is not so obvious, except when the coils of the spiral thread are very remote. In most 65. staminiaria. cases the spiral thread is. single, but it may be double, and sometimes —T™#ches. as many as twenty form a ribbon (Banana) and can be unrolled together. Finally, a spiral thread, which was originally single, may become folded and broken up into finer-threads (Beet-root).
Annular vessels (fig. 664) are membranous tubes girt within by rings, which
118 ANATOMY.
may be incomplete, or spirally twisted (fig. 665), whence they have been mistaken for old trachez ; they, however, differ from trachee in that they never present in their earliest condition a regular and continuous spiral, and that many intermediate forms between the ring and the spiral occnr in every such vessel ; as, however, they termi- nate in tapering cones, they have evidently the same origin as the trachee. Reticulate vessels are a modification of the annular; if rings are so placed as to touch at intervals, they resemble a network, and the same vessel may be both annular and reticulate (fig. 666). Striate vessels are membranous tubes, cylindric or pris- matic, the inner membrane of which resembles a web, whose interstices form thin more or less regular strie. In prismatic vessels (fig. 667) the striae extend to the angles, and the interstices resemble
SS the rungs of a ladder, S whence their name
7
of scalariform vessels. Striate vessels ori- ginate as a series of
im
K | superimposed ells ;
= others as fibres,
S as shown by their
: = spindle-shaped ends.
essels (fig.
664. Melon. 665. Melon. 666. Melon. 667. Brake. 668. Melon. Dotted Vv ( os Annular Spiral and Reticulate and Rayed prismatic Punctate monili- 668) are membranous vessel. annular vessel. annular vessel. vessels. form vessel.
tubes of which the inner membrane is perforated by small holes forming parallel series of oblique or horizontal dots; the vessel presents equidistant constrictions corresponding to circular folds in the interior, clearly indicating that the punctate vessel is formed by superim- posed cells of which the connecting surfaces have been absorbed. Punctate vessels with deep /; constrictions resemble chaplets of beads, whence 3 their name of moniliform or beaded vessels. Laticiferous Vessels.— We have seen that proper vessels present inequalities resulting from the 4 modifications of the inner membrane; there are others with smooth transparent and homogeneous walls, which contain a peculiar juice named the latea (fig. 669); these anastomose, and form a 4 complicated network, of which the tubes meet at right or acute angles; these tubes are usually 1{2,,Chetigonium. cylindric, and swollen here and there (fig. 670), 670, Dandelion. . . . Laticiferous vessels, from the accumulation of latex in certain places; below these swellings the vessel is gradually constricted, and the communication between the constricted and swollen portions is interrupted. The laticiferous vessels
ELEMENTARY ORGANS. 119
are thus distinguished from proper vessels by their transparent walls and by branching.
Union of the Elementary Organs.— Botanists are divided in opinion as to the forces which cause the walls of the elementary organs to cohere; some think that the walls of the cells are originally semi-fluid, and hence become agglutinated, and remain so even after the plant has ceased to live; others consider that an inter- cellular secretion cements the adjacent cell-walls. A tbird opinion is that vegetable tissue originates as a homogeneous plasma, which gradually thickens, and ends by forming vacuoles, which afterwards become the cavities of the cells; a common septum therefore separates the neighbouring cells; but soon each cell becomes individualized, the septum doubles more or less completely, and the cohesion between the cells is due to an interposed cellular tissue. This theory differs from the second, inasmuch that in the latter the cells are cemented by a subsequently secreted matter, while in the former the cells are united by an unorganized tissue, developed cotemporaneously with themselves; this unorganized tissue then itself becomes cellular, and finally separates the previously individualized cells which it originally united. Communication is established between elementary organs in various ways; it has been stated that it takes place by means of the destruction of the contiguous surfaces of cells and fibres placed end to end, from which there results a vessel ; communication can also be established through the walls of cells, either by the disappearance of the outer membrane, or by slits or holes at different points of its wall, or simply by pores rendering these membranes permeable.
Contents of the Elementary Organs.—The contents of these are very various: gaseous, liquid, or solid. Cell-contents appear as scattered or agglomerated granules, which in very young cells usually assume a lenticular form, and rest against the wall, or are even buried in its thickness (fig. 654) ; this body (the nucleus, cytoblast, or phacocyst of the cell) is regarded by botanists as a germ which, by its development, will produce a new cell. In most cases the nucleus becomes less distinct as the cell develops. According to the recent labours of M. Hartig, the nucleus is principally formed of small particles of matter analogous to albumen, a certain number of which are transformed into vesicles, which again give origin to cellulose, fecula, chlorophyll and aleurone. Cellulose is an insoluble substance forming the cell-walls, fibres, and vessels, the composition of which is. identical in all plants. Woody tissue or lignine is nothing but the thickened and condensed cellu- lose ; to its density wood owes its hardness; the stony particles in the flesh of pears and the stones of fruits are also formed of it.
Fecula or starch may be recognized by its blue-violet tinge when acted on by iodine, by its insolubility in cold water and its coagu- lation in hot water; its chemical composition is that of cellulose. Starch-grains are generally spheroidal or irregularly ovoid (fig. 671) ; their surface presents concentric circles around a point which usually occupies one of the ends of the granule. These circles indicate so 671. Pen. many layers, superimposed around a small nucleus; thus the se starch-grain is developed from within outwards, that is, in the reverse way to the cell
120 ANATOMY.
which contains it. Starch-grains may be easily examined by moistening a slice of cellular tissue containing them; a drop of iodine will then colour the starch- grains blue-violet, and bring out clearly the distinction between the cell and its con- tents. If there be grains of albumen accompanying the starch-grains, the iodine will colour them brown or yellow.
Chlorophyll or chromule is a green substance, which forms flakes of a gelatinous consistence floating in the colourless liquid of the cells; these flakes have a tendency to gather around or collect on the inner cell-walls, or on the contained starch or aleurone grains. Chlorophyll constitutes the green colour of plants; it is dissolved by alcohol, whence it has been supposed to be of a resinous nature.
The yellow colouring matter of cells is similar in consistence and properties to chlorophyll; but red, violet, or blue colouring matters are always liquid. ¥
Alewrone abounds in ripe seeds, and is always found either in the embryo or albumen. MHartig considers an aleurone grain to be a vesicle with a double aipHDEanS 2 Canalis a colourless waxy mass, which is coloured yellow by iodine,
mm and is ordinarily soluble in water. In certain plants it assumes a well-defined crystalline form (figs. 674, 675); in others, the nucleus of the aleurone mass has crystal- lized, while the surrounding layers remain amorphous, and thus the grain presents a round or ovoid ee ee form. Aleurone is essentially Cell containing crystals of
aleurone, in the midst formed of substances which ‘are of cells containing chlo-
collectively termed protein (for oi : which see the section on Vegetable Physiology). cute et Cakcatwinmg According to Hartig, the particles of the nucleus aces =eneRe undergo the following transformations : 1, the nucleus is transformed directly into chlorophyll, fecula, or aleurone; 2, it is transformed into starch and the starch into aleurone; 3, it is transformed into chlorophyll, and that into starch, which again passes into aleurone.
The laticiferous vessels contain a large quantity of powdery granules, which float in the latex, some of which are very large and colourless, and partake of the nature of starch.
As to the sap which fills these cells, and rises in the vessels, it is a colourless liquid, holding in solution the materials for cell-formation and cell-contents. The other liquids, either contained in the cells, or in the intercellular spaces, are fixed or volatile oils, turpentines, sugar or gum, dissolved in water. Finally, we find gases occupying the intercellular spaces, sometimes at considerable depths.
Besides the solid organic substances above described as occurring in the cellular tissue, special cells occur, containing mineral substances, the elements of which, either compound or simple, have been carried up by the sap, and have cry- stallized in the cells. Those of which the elements were originally in combination
672. Beet. Cells enclosing agglomerated
crystals.
ELEMENTARY ORGANS. 121
would crystallize at once; but for the others, it is necessary that the elements which have a reciprocal affinity should be united in proper proportions. In all cases, it is only during life that this crystallization is carried on, for the crystals are found in special cellular tissues, the forms of which determine theirs; the same salt being, in fact, found to crystallize very differently according to the tissues in which it is formed.
The crystals contained in the cells are either solitary or clustered; in the latter case they are grouped into radiating masses (fig. 672), or bundles of parallel needles (fig. 673) named raphides (rR); and they may often be seen escaping from the cells (c) when the tissue containing them is dissected under the microscope. Finally, the cells and even the intercellular spaces often contain silex, one of the most abundant of minerals, which constitutes sand and flint; this silex even encrusts the tissues of certain’ plants, and notably the straw of Graminew. Certain mineral concretions are observable in the leaves of some Urticew; if the leaf of a Nettle be viewed with a lens, transparent spots may be distinguished ; this is due to the presence of calcareous particles deposited in the outer cells, to which Weddell has given the name of cystoliths. These cystoliths differ from the crystals represented in fig. 672, in being deposited in calcareous layers around a nucleus fornied at the expense of the cell-wall, which has been pulled aside by the accumulation of mineral matter, and has lengthened into a very delicate pedicel from which the cystolith is suspended. This formation may be compared with that of stalactites.
Epidermis.— Before treating of the anatomy of the fundamental organs, we shall describe the epidermis, which covers the surface of the vegetable. If the leaf of a Lily or Iris be torn, a shred of transpa- rent colourless membrane is detached from one of the fragments, together with some cellular tissue, filled with green chlorophyll; a simple lens shows on this membrane several parallel (fig. 676) or reticulate lines (fig. 677) and small, more opaque spots. Under a microscope, it is seen to be com- posed of large flat cells, which may be hexagonal or quadrilateral, or irregularly waved, and which contain a colourless liquid; their lateral walls are closely united, whence the solidity of the epider-
Bpidennicantviomata. mis; their lower surface slightly adheres _, 677, Balsam.
Epidermis and stomata.
to the subjacent cellular tissue; their exposed walls are usually thicker than the others, and may be flat or raised in the centre, according as the surface of the epidermis is smooth or rough.
In most cases, the epidermis is composed of a single layer of cells; when there is a second, it is usually formed of much smaller cells. The lateral walls of all the epidermal cells are not contiguous ; many of them present interspaces, occupied by little bodies resembling a button-hole with a double rim or border (figs. 676, 677),
122 ANATOMY.
formed of two curved cells whose concavities face each other. These two small lip- like cells are termed stomata. Stomata, though epidermal organs, differ from the epidermis in that their cells are much smaller, and nearly always situated below those of the epidermis ; they further present different contents, and especially granules of chlorophyll ; whence they may be regarded as intermediate between the epidermis and the subjacent parenchyma.
Stomata are variously distributed over the surface of the leaves : usually solitary,
often arranged in series, some-
ee OOO OO SS Sa times crowded in the base of
See Soa AK ni NN iN es? a cavity (as in some Proteacee, RGN AN a figs. 678, 679). Their number ve aN wu =i ; ; Ewe es ne =i varies: the Iris contains Pilih: sins 12,000 in a square inch; the Pink, 40,000; the Lilac, 120,000. When moistened,
679. Part of a Banksia leaf, presenting three sections
their lips swell and become more curved, and hence gape ; when dry, they shorten and close.
Stomata always correspond to intercellular passages, and are found on the ordinary leaves of Phenogams, principally on their lower surface, on stipules, on herbaceous bark, calyces, and ovaries; they are wanting on roots, rhizomes, non- foliaceous petioles, most petals, and seeds ; acotyledons, and submerged aquatic plants, which have no epidermis, equally want stomata.
If a fragment of a stem or leaf be macerated, the cellular tissue beneath the epidermis is rapidly destroyed, and the latter divides into two layers, an external epidermis proper, and a very thin membraue (fig. 680), moulded on the epidermis and extending even over its hairs, which are sheathed in it like fingers in a glove (P); it presents openings (F) corresponding to the stomata. Brongniart has called this membrane the cuticle (little skin); it is not cellular, like the epidermis which it covers.
parallel to the lower sur- face, and at different depths (mag.).?
678. Vertical section of part of a Banksia leaf (mag.)."
680, Cabbage.
Cuticle.
! Fig. 678 is a section perpendicular to the thickness _leaf, carried through three such depressions, each circum~
of the leaf, showing: 1, on the upper and lower faces two layers of epidermal cells ; 2, fibro-vascular bundles to the right and left, cut perpendicularly to their length; 3, on the lower face, a depression, clothed with hairs, and pierced by stomata which communicate with the interstices of a very loose cellular tissue. Above this ‘tissue, the upper half is a mass of elongated and erect cells, perpendicular to the epidermis.
2 Fig. 679. Three sections parallel to the plane of the
scribed by the fibro-vascular bundles of the nerves. In the cavity at the bottom of the figure, the section has carried away the hairs clothing the walls of the depres- sion, leaving. the stomata and epidermal cells visible; in the cavity on the right the loose cellular tissue which underlies the stomata of the epidermis is seen through the latter; in the third depression the section has re- moved all but this subjacent tissue with its intercellular spaces,
FUNDAMENTAL ORGANS. 123
The cuticle is more constantly present than the epidermis; submerged plants and acotyledons are clothed in it; and some botanists have considered that it should be regarded as the true epidermis. Its formation is attributed to the overflow of that intercellular secretive tissue which we have already spoken of as spreading itself upon all the organs, and which deposits a sort of varnish or continuous layer over their outer surface. Recent experiments. of Frémy seem to show that the chemical composition of the cuticle is analogous to that of india-rubber, which makes it a suitable protection for the underlying tissues. Frémy has also discovered that
woody fibre is sometimes clothed with a cuticle similar to that which clothes the epidermis.
FUNDAMENTAL ORGANS.
We shall now describe the anatomy of the fundamental organs in succession ; ie. the vegetable axis (stem and root), and its lateral expansions (leaves, sepals, petals, stamens, carpels, ovules). We have described the embryo as a diminutive plant, from which all the parts enumerated above will be developed ; we must there- fore first describe its structure, and then trace its stages of development from its birth till it becomes a plant similar to its parent.
_ The embryo invariably commences as a cell with granular contents. In cotyle- donous plants, this cell does not retain its form and structure; from spherical it becomes oval; then at one of the extremities, if the plant is monocotyledonous, a rounded lobe (cotyledon) appears, obliquely and laterally to the axis; if dicotyle- donous, two lateral lobes (cotyledons) appear, crowning the axis; the elongated summit of the axis becomes the plumule; from the opposite end the radicle will be developed, and the body of the cellular mass will form the caulicle. Following the growth of these fundamental organs, we begin with the stem, which differs remark- ably, according to whether the embryo is mono- or di-cotyledonous.
Stem of Dicotyledonous Plants.—Take the Melon as a type. In the caulicle, which before germination is entirely cellular, some cells elongate into fibres ; certain of these fibres, together with other super- imposed cells, break the transverse walls which separated them, and become vessels. This change takes place in definite posi- tions, and a horizontal section of the stem (fig. 681) will show in the centre a disk (m) of large, loose, nearly transparent polyhedral or spheroidal cells; at the circumference, a ring of dark green, more closely packed cells; communication being established between this ring and the disk by radiating ree bands of cells (rm), extending from the centre to the cir- Hoviepetel es ot the stem cumference, and dilating in the same direction; the whole resembling a wheel, of which the tire is the circle, the axle the central disk, and the spokes the radiating bands. Between the disk and the circle, and separated by the bands, are wedge-shaped plates, which together form a. circular group, and consist of fibro-vascular tissue, and vessels which have been formed in the middle of the cellular mass, and become united into bundles. The gaping
124 ANATOMY.
mouths of these vessels and fibres are very evident, as is the relative thickness of their walls: we shall return to this immediately. The cellular tissue of the ring, disk, and bands, constitutes the medullary system. The medullary system of the disk (m) is called the pith; that of the ring is the cortical pith; and the radiating cellular bands (xm) are the medullary rays. The wedges of fibres and vessels, separated by the rays, are the jibro-vascular system. If we now dissect one of the bundles in a well-formed stem of Melon, whose duration is annual (fig. 682), it is found to be tolerably stout, and completely surrounded by the cellular tissue, the pith (m), bark (pc), and medullary rays (RM). Beginning from the interior, we find, 1, spiral vessels (7), and opaque white fibres with thick walls; 2, fibres (F) with thinner walls, and consequently larger cavities, arranged in series, and altogether occupying half of the wedge; together with annular, rayed, and dotted vessels (v Pp), recognizable, especially the latter, by the size of their walls ;
Mees 3, a greenish cellular tissue (c); 4, Tceesee : thick-walled fibres (L) like those next RM... the pith, but more abundant; 5, some branching (laticiferous) vessels (v1) Pied with soft walls; 6, the cortical paren- VP... chyma (Pc), covered by a membrane (£) =s consisting of the epidermis and cuticle. Baar In a horizontal section of the stem (fig. L... Uday) 681), the trachez (7) and fibres next the Vi. aNe, pith form with the neighbouring vessels ‘ hice a ring (interrupted by the medullary | E> rays), which has received the collective
682. Melon. name of medullary sheath; the fibres |
Hori tal sli yf yf : : the Ales vascsiae bunds OUtSide this sheath are the woody.
of the stem (mag.).
fibres; the outer fibres, separated from ~ the former by a cellular zone, and resembling those of the medullary sheath, are the woody fibres of the bark; > finally, the cellular zone which separates the cortical from the woody fibres is called the cambiwm layer. In 683, Maple.
the Melon, this zone dies each year, together with pi.yascwr bundle of the stem ot the the fibro-vascular bundle, which it divides into two VY 2n4 vertical sections (mag.). unequal parts; but in a woody-stemmed, and hence perennial plant (Oak, Elder), fresh layers are annually formed in the thickness of this zone, by which the thickness of the stem increases. Young branches, therefore, one or two years old or more, must be examined, to trace the further development of the wood and bark. A fibro-vascular bundle in a one-year-old branch of Oak, Elder, or Maple (fig. 683), coincides in structure with that of the Melon stem; but in the cortical system (Pc) there will be found, between the epidermis and central layer of cells, a layer of close-set cubical or tabular cells (s); these contain no chlorophyll, are white or brown, and are readily distinguishable from the subjacent cortical cells, which are
polyhedral, coloured by green granules, and separated by numerous interstices. This
FUNDAMENTAL ORGANS. 125
3
layer is the suber, which in certain trees attains a considerable development, and forms cork. Take now a vertical section of the same branch, and the disposition, &c. of the fibres and vessels will appear as in fig. 683.
The cambium, which does not become organized in annual or herbaceous stems like the Melon, in perennial stems becomes highly organized (fig. 684). During the 4 second year, this gelatinous s tissue undergoes the following changes: outside the woody
chasis es
SOse
oS,
ec 0;
a <=) 228
rc, 0 Sez
i
eae et wast
5
a ae en
5S. PL.PL LSP LMO.G.F OVOP. V.E.v.nTM,
; 684, Maple. Horizontal slice, showing the development of a woody bundle ina three- year-old branch. Cc, cambium layer, separating the wood from the bark. 1. Pith (Mt), traches (T), punctate vessels and fibres of the first year (V).—
2. Punctate vessels (v) and fibres (1) of the second year.—3. Vessels (v) and fibres of the third year. Within the bark (s) is seen the cortical layer of
the first year (P. L), then that of the second year (P. L), and of the third year ? _ 685, Oak. (P.L), separated by the cambium (c) from the contemporaneous woody Horizontal slice of a twenty-five years layer (mag.). old trunk.
fibres interspersed with large vessels (1. v), is formed one fresh cambium layer (2. F, V); within the fibres of the liber and of the cortical system another is formed; these layers become moulded upon the older ones, and the zone of cambium which is transformed to produce them presents a cellular organization at those points, which corresponds to the cells of the medullary rays, so that these continue without interruption from the pith to the cortical layers.
Each ring of vascular bundles was hence from its earliest condition enclosed in two cambium layers, of which one belongs to the wood, the other to the bark; each of these vascular bundles, again, is in its turn separated by a cambium layer, which in the third year repeats the process, producing within ligneous fibres (3. F) and large vessels (3. v), and outside liber (L) and cortical parenchyma (P), and so on each year. Now, each wood bundle being composed of two elements, and the large- sized vessels being usually towards the interior of the bundle, we can, by counting their number (which is easily ascertained by the gaping mouths of the large vessels), reckon the number of annual layers, or, in a word, the age of the stem or branch (fig. 685).
It must be remarked that the secondary ligneous bundles differ from the primary in the total absence of trachee ; these vessels being confined to the medullary sheath.
We have said that the medullary rays are not interrupted by the formation of new vascular bundles, because the cambium zone remains cellular at the points corresponding to these rays. If each newly formed bundle was undivided, like that in juxtaposition with it, the number of medullary rays would be always the same ; but this is not the case; at the circumference of the primitive bundle one or more longitudinal series of cells is developed, which reach to the circumference, and
126 » ANATOMY.
divide the new bundle into two or three parts (fig. 686). These cellular rays (2, 8, 4), which are termed secondary medullary rays, to distinguish them from the primary (1), which start from the pith (a), are thus doubled in each annual ring, and, like the large rays between the fibro-vascular vessels, form a sort of vertical septa or radiating walls, com- posed of elongated and super- imposed cells; whence the name of muriform tissue for the me- dullary rays.
686. Cork Oak. . : . Horizontal slice showing the development of two woody Hence, in its totality the bundles in a four-year-old branch (mag.). sg t em pr esen: ts two very dis tine t
systems, the woody (weod), and the cortical (bark). 1. The woody system
is formed of the central pith and zones of fibro-vascular bundles, sepa-
rated by medullary rays. The innermost of these is the medullary Rnisoptiva,
sheath, formed of trachee and fibres analogous to the liber, and “7 outwardly composed of woody fibres and rayed, annular, and dotted vessels. The other zones are similarly organized, except that they never possess trachem. 2. The bark system is formed of the epidermis, the cork, the endophleum, and the bast fibres (liber), external to and amongst which the laticiferous vessels ramify. With age the cells of the pith lose colour, dry, separate, and finally die; the woody fibres thicken, and usually darken; of these the heart-wood (duramen) differs from the more recently formed or sap-wood, which is more watery, softer, and brighter coloured. The liber fibres (fig. 686 bis) are more slender, longer, and more tenacious than the woody fibres ; and are of great use in the manufacture of thread, cord, and textiles. Their bundles descend vertically and rectilinearly in thin concentric plates, whence their name liber (book) ; but in some plants, as the Oak and Lime, they form a network, the interstices of which are occupied by the medullary rays.
From the mode of development of the wood and bark systems, it is obvious that the wood must harden, and the bark decay ; for in all the bark tissues, the later formed are constantly pushing towards the periphery, within which they have been developed; this produces the exfoliation of the several elements of the cortical Sys- tem; the epidermis first, then the cork-cells, the endophleum, and sometimes the liber.
It is not necessary to describe any of those anomalous dicotyledonous stems which present peculiar tissues or hyper-development of certain elements, or the absence of others ; except that of Conifers (Pine, Fir, Larch, Yew, &e.), the wood of which, with the exception of a few trachese in the medullary sheath, is entirely com- posed of regularly dotted fibres. The walls of these wood-fibres (fig. 687) are hollowed into small cups, like watch-glasses, which are arranged in two straight lines, occupying the opposite sides of each fibre. These cups are so placed in con- tiguity that their concavities correspond (fig. 688), leaving an interposed. lens-like
FUNDAMENTAL ORGANS. 127
space. The dot is placed in the centre of each cup (and corresponds to a thinned portion resulting from the absence of the inner membranes) ; from this thin portion there proceeds, on the convexity of each cup, a short canal, with only one opening, which leads into the interior of the fibre. The lens-shaped cavity arising from, H..rm the contact of two fibres is usually filled with resin (turpentine), which infiltrates into the cavity of the fibres and destroys them by degrees; the result is those
resinous deposits which are often found
ptt occupying large cavities in the wood of cl conifers (fig. 689, la). Seer vs & ; 688. Pine. Vertical section of the stem (mag.). p. f, 687, Pine. ' 689. Pine, fibre wall; c.1, lenticular cavity; r.m, Punctate fibre Horizontal slice showing the development of two woody medullary ray; c. f, cavity in a fibre. (mag.). bundles in-a three-year-old branch (mag.),
Stems of Monocotyledons.—When the monocotyledonous embryo, which is entirely cellular before germination, begins to elongate, fibro-vascular bundles form in its stem. These are at first arranged in a ring as in young dicotyledons; but soon, as the leaves develop, the bundles multiply without any apparent order in the cellular tissue, becoming more numerous and close as they approach the circumference of the stem. If a fully developed bundle be examined under the microscope (fig. 690), it is oviuoiita aaa oF tie stem. found to be structurally identical with that of a dicotyledon; beginning from the central pith, we find walled fibres analogous to liber (1), then trachee (1), then, mixed with cells (Pp), some of which elongate and thicken into fibres, are seen the openings of rayed or dotted vessels (v): the circumference of the bundle is formed of thick- walled fibres (léber, tL), outside of and amongst which the
690. T ti f fibro- eos . vascular bundle of « monocoty. laticiferous vessels ramify (v.L).
Eee ees a a Eo But, though individual bundles resemble those of a first eerie year’s dicotyledonous stem, when taken all together they pre-
sent a very important difference (fig. 691), in not being grouped in concentric zones but
128 ANATOMY.
(F) remaining isolated and scattered through the medullary system (m) without any medullary rays of muriform tissue. Here there is no symmetrical arrangement ; the bundles are scattered throughout the pith, and may multiply without being impeded by lateral pressure; further, each remains simple; at no period does it develop between its bark and wood systems a layer of cambium destined to form new bundles. In dicotyledons, on the contrary, the bundles are pressed into zones from the first year, and their wood and bark systems being concentric, they can only multiply by fresh wood and bark bundles being formed between them. The consequence of this arrangement of the fibro-vascular bundles is, that in dicotyledons the stem is hardest towards the centre, whilst in monocotyledons the stem is hardest towards the circum- ference; as is very apparent in the woody (fig. 692), and even in the herbaceous stems of monocotyledons. In a longitudinal section of a woody (fig. 693) or herbaceous (fig. 694) monocotyledonous stem, those differences are still more apparent; starting from the insertion of a leaf, each bundle descends at first obliquely inwards, then vertically, then again obliquely outwards; cros- sing in its path all the bundles which have origi- nated below it, and are hence older than itself, and ending by taking up a
Dil ie : 694. Tris. 692. Palm. 693. Theoretical section of a position outside of them Stem cut Stem cut vertically. Palm stem. vertically.
all. In dicotyledons also, . the youngest bundles are the outermost, those of the same age follow nearly parallel; but whereas in their courses they unite so as to form a cylinder, in monocotyledons they diverge below and converge above. The composition of mono- cotyledonous bundles also differs in different parts of their course, the wood system predominating over the cortical in the upper part, where it descends obliquely inwards, the cortical system predominating in the lower part, where it descends obliquely outwards, and finally the cortical system alone being developed where the bundle reaches the periphery. Here the bundle becomes more slender, and divides into thread-like branches, which interlace with those of the neighbouring bundles, and form together, within the cellular periphery, a layer of fibres comparable, according to many botanists, with a liber zone.
It is obvious that these fibro-vascular bundles, being composed of different 2lements at different heights, and becoming so slender towards the periphery, must appear very dissimilar in a horizontal cut of the stem; the scattered small bundles with large vessels, which occupy the middle of the stem, are the upper portions of sundles in which that which we have called the wood system (though it is rather
FUNDAMENTAL ORGANS. 129
cellular and vascular than fibrous) predominates. The coloured and dense bundles, which form a more solid zone towards the periphery, are the lower portions of bundles in which fibres analogous to liber predominate; and, finally, the less compressed bundles which are usually seen outside of the coloured zone are these same fibres after having branched and spread out, and before being lost in the periphery, which is a cellular zone representing the bark.
A monocotyledonous stem usually retains about the same diameter throughout. This is because the fibro-vascular bundles, gradually attenuated towards their lower extremity, do not, as in dicotyledons, unite and descend to the bottom of the stem ; hence, any two truncheons of a monocotyledonous stem, being equally rich in bundles, can differ but little in diameter. d
Root.—In the embryo, the radicle is the simple cellular lower end of the caulicle, which elongates downwards as the latter ascends with its plumule and cotyledons. A monocotyledonous seed usually presents several radicles (fig. 642); these are not, however, naked like those of dicotyledons, but are originally enveloped in an outer layer (serving as bark), which they push forward and pierce, emerging from it as from a sheath; whence the name of coleorhiza for this organ (fig. 642).
Examples have been given of stems emitting accessory or adventitious roots from various parts of their surface; the structure of these is precisely the same as that of the radicle ; and they may even be regarded as identical, the radicle being con- sidered as a production of the caulicle, and all roots, whether primary or secondary, as adventitious.
In its earliest stage the root presents an axis of densely ¢p | packed cells; the central of these elongate and form vessels which interlace with those of the stem (fig. 695). The root may be simple or branched, but its branches do not start from the axil of a leaf, and are not regularly arranged, like the shoots of ©... the ascending axis. They terminate in fibrils, together called root-fibres, which decay, and are replaced by fresh ones which usually spring from near the base of the youngest branch. Like the stem, the root-branches and fibres are clothed with an epidermis or cuticle, except at the tips, which some botanists call spongioles (sp). The root elongates at the tips of its branches, but not of its root-fibres, which are caducous; and as \ the fresh cells of the root-branches are at first deprived of sp... epidermis, it is supposed that roots absorb moisture from the soil x by these, as well as by their root-fibres. Vertical section afm rootlet,
The fibrous and vascular tissues of roots are the same as Gaerne peie ee those of stems, but no trachee are ever found in them; the ing wees ters GP
é 7 Par : +, bottom, more recentlyf d, cells are distended with juice or filled with fecula (Orchis, constitute the spongicle (Sr).
fig. 695).
In dicotyledons, the root is distinguished from the stem by the absence of pith and medullary sheath, and by its axis being occupied by woody fibres ; there is scarcely an exception to this. Its diameter increases, like that of the stem, by the annual
K
uh
i
na
ane
a a
130 ANATOMY.
formation of two concentric zones between the wood and bark; it elongates at its extremity only, while the stem and its branches elongate throughout their length; this may easily be proved by marking off an inch of a root and an inch of a stem. Monocotyledons, instead of having a tap-root (i.e. one main axis which branches), usually emit compound roots, i.e. composed of simple or slightly branched bundles, rising from the neck. Their anatomical structure is exactly similar to that of stems.
Leaves.—The anatomical structure of leaves is the same as that of the stem; they consist of a fibro-vascular bundle and parenchyma; this bundle, which is wholly formed before leaving the stem, spreads into a blade as it emerges (sessile leaf), or remains undivided for a certain distance before expanding (petiolate leaf) ; the nerves of the blade are formed of fibres and vessels; both it and the petiole are covered with a layer of epidermis bearing stomata on every part except the nerves and petiole. The petiole, before expanding, often forms a sheath or stipules; the
sheath exists when the Pa | m partial bundles of which it is composed separate from B each other, but without \ §, diverging; the stipules are NACHT the result of the divere- \ 2D ence of the lateral bundles \ of the petiole.! Where the fibro-vas- cular bundle (fig. 696, Fv) A iepermiae ISy leaves the stem to form the petiole (F), the fibres composing itare shortened,
cl FVM 696. Branch cut vertically,
697, Melon. showing the petiole spring- gnd narrowed at each end, Section perpendicular to the surface of a leaf (mag.).
P, hair; sv, stoma; F.v, fibro-vascular bundle; rs, whence their surfaces of upper epidermis ; Ei, lower epidermis,
contact are contracted; they are hence not solidly united at the point of emergence ; and it is this defective cohesion which causes the fall of most leaves. The stem presents a little swelling at the base of the petiole, called the cushion (c), which is visible after the disconnection of the petiole (fig. 54), together with the scar (Fr) left by the petiole. The relative position of the elements of the fibro-vascular bundle which passes from the stem into the leaf, shows clearly that the leaf-blade may be compared to a flattened stem, the fibres and vessels of which have been spread out, and thus allowed plenty of room for the development of parenchyma between their ramifications. As in the stem the fibro-vascular bundle consists of trachez in the centre, then rayed or dotted vessels and woody fibres, and on the outside laticiferous vessels and thick-walled liber-fibres, so in the leaf- blade each nerve (which is a partial bundle) presents trachez on its upper surface, rayed or dotted vessels with woody fibre on its lower surface, and laticiferous
ing from the stem (mag.).
1 This theory of the origin and development of stipules requires considerable modification.—Ep.
FUNDAMENTAL ORGANS. 131
vessels and liber-fibres. The lower surface of the leaf, which corresponds to the cortical system, is generally more hairy and presents more stomata than the upper, which corresponds to the wood system. The parenchyma of the leaf, filled with green chlorophyll, usually presents (fig. 697), in flat leaves, two well-marked divisions; the upper, belonging to the woody system, consists of one or more series of oblong cells (P.s), arranged perpendicularly side by side beneath the epidermis (z.8), leaving very small interspaces (m); the lower division, belonging to the cortical system, consists of irregular cells (p.i), with interspaces (L) corresponding with the stomata. The parenchyma of fleshy leaves (as Sedum) consists of cells with few interspaces, which cells become poorer in chlorophyll towards the centre of the leaf. Submerged leaves (fig. 698) have no epidermis, stomata, fibres, or vessels; their parenchyma is reduced to elongated cells, arranged in few series, and is consequently very permeable by water.
The leaf originates as a small cellular tumour, which afterwards dilates into a blade, the cells on the median line of which elongate and form fibres, then, as in the stem, first trachee, and lastly other vessels. %
In his treatise ‘On the Formation of ey
the basifugal, basipetal, mixed, and parallel.
‘i 5 698. Potamogeton. In the basifugal, the leaf is developed from _ Section perpendicular to the surface of a leaf (mag.).
a P, parenchyma without epidermis ; v, interstices. below upwards, ie. the oldest parts are
those at the base of the leaf, and the tip is the last part formed; the stipules appear before the leaflets and secondary nerves of the leaf. In the basipetal type, the rachis or axis of the leaf appears first, and on its sides the lobes and leaflets spring from above downwards; the tip is hence developed before the base. The stipules are developed before the lowest leaflets, and sometimes even before the upper. In this type, not only the leaflets, but their secondary nerves and teeth, appear in succession downwards. In the mixed arrangement, both these types are followed. In the parallel type the nerves are all formed in parallel lines, but the sheath appears first. The elongation of the leaf takes place at the base of the blade, or base of the petiole. The sheath, although the first formed, does not increase till the leaf has developed to a certain extent.
The nerves of leaves are arranged very differently in monocotyledons and dicoty- ledons. In the former (fig. 33), they are usually simple, or, if branched, the branches do not inosculate. In dicotyledons, on the contrary (fig. 6), the nerves branch into veins and venules, which inosculate with those of the neighbouring nerves, and form a fibro-vascular network of which the interstices are filled with parenchyma. Nevertheless, in some monocotyledons, the basal nerves are not all parallel and simple; but secondary nerves spring from one or more of the principal nerves, and diverge in other directions; but these secondary nerves are parallel, and the con- vexity of the arc which they describe is turned towards the principal nerve (this nervation is rare among dicotyledons); lastly, the nerves in monocotyledons may
x 2
132 ANATOMY.
anastomose into a network, and the blade, instead of being entire, as is usual in this class, may be lobed (Arwm). On the other hand, some dicotyledons occur with parallel and simple nerves; but these exceptions do not invalidate the general rule indicated above. In all cases of determining the class of a plant, the examination of the nerves must be supplemented by that of the fibro-vascular bundles of the stem, which are symmetrically arranged in dicotyledons (fig. 685); and dispersed without order, though more closely packed towards the circumference, in monocoty- ledons (fig. 691).
Buds.—The bud (fig. 696, B) appears at first under the bark as a cellular point continuous with the extremity of a medullary ray; it soon pushes through the bark, and forms a tumour on the stem, when its cellular tissue becomes organized into fibres and vessels communicating with those of the stem; the medullary sheath, however, of the young branch is closed at first, and does not communicate with the medullary ray of the axis from which it emanates.
Sepals.—The anatomical structure of these organs completes the analogy between them and leaves. The nerves of the sepals are bundles of trachee and fibres, parenchyma is spread out between them, and their surfaces are covered by an epidermis, of which the upper presents more stomata than the lower. As with the leaves, the nerves of the sepals are usually parallel and simple in monocotyledons, branched and anastomosing in dicotyledons. The sepals first appear as small cellular papille, connected at the base by an annular disk referable to the recep- tacle; their tips are free in both the monosepalous and polysepalous calyx; it is only later that the calycinal tube appears. Vascular bundles are gradually tormed in the sepals as in the leaves.
Petals——The corolline leaves have often, like ordinary leaves, a petiole, which is called the claw. When this is present, the fibro-vascular bundles traverse its entire length, and only separate to form the nerves of the blade; these nerves, usually dichotomous, are composed of trachee and elongated cells; the parenchyma which fills their interstices is formed of a few layers of cells, covered by an epidermis presenting very few stomata on the upper surface only, or none at all.
Very young petals, like sepals, appear as cellular papille ; but in petals these soon dilate, and form dark or light-green disks, which at a later period always change colour. Although the petals are placed below the stamens on the floral axis, they generally expand later, as if they had been developed later, which is not the case.
In a monopetalous corolla, the torus is raised above its ordinary level so as to form a little circular cushion which connects the leaves to which it gave birth, and the segments of the corolla appear as projections upon this cushion.
Finally, whether the corolla be monopetalous or polypetalous, its petals are developed like ordinary leaves; the tip and base are first formed, and the develop- ment takes place towards the central veins from below upwards, from above down- wards, and laterally.
Stamens.—The complete stamen consists of filament, connective, anther, and pollen :
FUNDAMENTAL ORGANS.
133
let us examine their structure in the adult, and their mode of development in the
young stamen.
The filament consists of a central bundle of trachez which traverses its length, of a layer of cells enveloping this bundle, and of a thin superficial epidermis. The connective, which is the continuation of the filament, is formed of cells of the con- sistence of glandular tissue, in which the bundle of trachee terminates.
The anther is usually divided into two cavities, separated by the connective, and
containing the pollen. The walls of these cells consist of an outer or epidermal layer of cells (fig. 699, cz) with many stomata, and of an inner simple or multiple layer of fibrous (z), annular, spiral, or reticulated cells; this layer becomes thinner as it approaches the line of dehiscence of the anther, where it ends. At the period of dehis- cence the outer membrane of these cells is destroyed, and the little netted, ringed, or spiral bands which lined it alone enclose the pollen,
aE, CE... :
699. Melon. Remains of the fibrous cells lining the epi- dermis of the anther (mag.).
the emission of which they assist when they dry up, contract, and separate the valves of the anther. The young stamen appears as acellular green papilla, which usually turns yellow. The anther is the first formed; it presents a median furrow (the connective), and two lateral ones (the future lines of dehiscence) ; the filament appears next, at first wholly cellular, then traversed by a bundle of tracheze. The tissue of the anther is at first a uniform cellular mass (fig. 700), in the middle of which a certain number of cells are absorbed and leave usually four spaces, which gradually enlarge and form as
many cavities, nearly equidistant from the centre and the periphery.
these small cavities eventually represents an entire cell (fig. 701).
BOY
CAPSS
en ig adie, L ete) Ais Wace oe Ntzennelziee ts ‘i cs DOr
za c2 ct era Ox
a! ross nee A ag oes
x nae H Ry SHENG EONG
SY
KY
700. Melon. Vertical section of young anther (mag.), showing 701. Melon. the epidermal cells (CE), Vertical section of an anther- 702. Melon. and the inner cells (C1), cell (mag.) with two cellules. Vertical section of an anther-cell all alike and homoge- CE, epidermal cells ; c1, inner where the cellules are filled with - neous, in the middle of cells; CM, mother-cells con- mother-cells, cL, walls of the which spaces will form. tained in the cellules, cellules (mag.).
Each pair of All these four
703. Melon. Mother-cells (cM), originally hexagonal, of which the septa are destroyed, and con- taining each four pollen - grains (Pp) (mag.).
cavities gradually fill with mucilage, out of which are elaborated two forms of cellular tissue, one of small cells (fig. 702, ou) that line the cavity, the other of large cells (cm) that fill the cavity, and within which the pollen is developed. The latter, called mother-cells (cm), soon become filled with a fluid full of granules; the granules again aggregate, and form four nuclei floating in the liquid, which thickens by degrees from without inwards, and finally forms four septa dividing the mother-cells into as many cellules. Each nucleus then becomes coated with a membrane (fig.
184 ANATOMY.
703), after which both the septa and the walls of the mother-cells disappear, and the four nuclei (p) which filled them are set free as pollen-grains (fig. 704). As they grow (figs. 705 and 706), the cellular tissue of the anther, in the middle of which the cavities had been formed, are absorbed; a layer of cells which formed the walls of the cavities now lines the membrane of the epidermis (fig. 699, cz), and rapidly changes into a layer of fibrous
cells (#) ; the tissue which sepa-
©) C) ©) rated the small cavities becomes gradually thinner, and forms a
704. Melon. 705. Melon. 706. Melon. is c I Young pollen-grains, Nearly adult pollen Ripe pollen septum which projects from the free (mag.). (mag.). (mag.).
connective towards the line of dehiscence; this septum is soon destroyed, and the two cavities form but one (anther-cell). In some plants this septum is persistent, and the anther remains quadrilocular (Butomus, fig. 326). In many plants the remains of the mother- cells only partially disappear, and the rest connect the pollen-grains, as in Orchis (figs. 359 and 360), where an elastic network causes them to cohere in small masses.
Carpels.—The anatomy of the carpellary leaves is analogous to that of ordinary
708. Pear. ; 709. Pear. 707. Pear, Young carpels, seen from Young flower, cut vertically , Very young flower, cut within, at first concave, to show the growth of the 711. Pear, vertically to show the and the edges afterwards receptacle, the atrangemen’ Flower cttt vertically, with the petals, stamens and carpel- approaching to form of the carpels, and the inser- stamens and petals removed, show- Jary mamme free on the the style and placentas tion of the petals and stamens ing the carpels enveloped by the receptacle (mag.). (mag.). (mag.). ; receptacular cup (mdg.).
leaves; a cellular tissue (sometimes very succulent, as in berries and drupes), traversed by fibro-vascular bundles, is covered with an epidermis, the outer surface only of which bears stomata; the bundles ascend from the ovary into the style, occupying its circumference, its centre being hollowed into a canal. The inner walls of this canal, which is formed by the convolution of the upper end of the carpellary leaf, is covered with projecting cells, and its axis is occupied by soft cellular filaments, named conducting
710. Pear. tisswe ; it is this tissue which constitutes, on the top or sides of the Sree earn style, the true stigmatic tissue. The placenta, which transmits sa hae cept oir the nourishment to the seed, and the funicle, which is a prolongation he ee oo of the placenta, consist of a bundle of trachese surrounded by oes elongated cells.
Inferior ovaries have the carpels encased in a receptacular cup, which is some-
FUNDAMENTAL ORGANS. 135
times enormously hypertrophied, especially in Rosacee and Pomacee (figs. 707 to 711), and bears on the top the stamens, petals, and calyx.
Ovule.—Botanists often apply this name to the undeveloped seed; but, to be precise, they ought to confine it to the unfertilized seed.
To trace the development of the ovule, it must be examined long before the bud opens: it then appears as a papilla on the placenta, called the nucleus (fig. 712); around the base of the nucleus (fig. 713) a circular ring is formed (s), which at first grows at the same rate as itself, but, rising on its surface, it eventually overtops and finally almost entirely envelops the nucleus ; but before this takes place, a second circular ring is developed (fig. 714, p) outside the first (s), which follows it in its growth, and ends by reaching and overtopping it; the nucleus (Nn) is hence enclosed in two sacs, whose mouths are contracted, and on a level with its top, thus forming a little cylindrical or cup-shaped cavity, consisting of two superimposed rings touching at all points of their circumference. The upper opening, belonging to the outer coat, is named exostome (Ex); the a lower, belonging to the ie inner coat, is named en- dostome (End). The union of the endostome and ex- ostome constitutes the micropyle, which always cae a ittlcally corresponds to the top of eae a Ce 714. Polygonum. secundine ; N, nucleus }
ag). Ovule (mag.). S.E, embryonic sac.
the nucleus. The outer
coat is called the primine (P), the inner the secundine (s) ; the nucleus (nN) has also been called the ¢ercine; terms which refer to their order of superposition from without inwards, not that of development. The funicle (F) is inserted on the primine, and its contained bundle of trachew, after traversing the primine and secundine, expands at the base of the nucleus into a swollen coloured cellular tissue, termed chalaz«, opposite to which there is almost always a corresponding swelling on the primine. As the ovule, which is wholly composed of cellular tissue, grows, a cavity is formed near the centre (fig. 715) of the nucleus, by the dilatation of one of its cells; this cavity, which extends through the length of the nucleus, and adheres by its two ends to the neighbouring cells, is the embryonic sac (8.5), or quintine. Its walls shortly become lined with a mucilaginous cellular tissue, developed from the circum- ference towards the centre, which fills the cavity of the sac; this tissue, together with that of the nucleus, constitutes the alimentary deposit destined for the embryo, and is called albwmen (perispermum). The ovule, thus organized before fertilization, undergoes one of the three following changes :—most frequently the embryonic sac pushes away the nucleus on all sides, and its own parenchyma alone is developed, when the albumen is more or less fleshy; sometimes, on the contrary, the nucleus presses upon the embryonic sac, and reduces it to a narrow tube, when the albumen is farinaceous ; sometimes, again, the action is reciprocal, and two kinds of albumen result,—the white Nymphea (figs. 610, 647) affords a remarkable instance of this. For this reason Gaertner, comparing the ovule with a bird’s egg, limited the term
715, Polygonum.
136 ANATOMY.
clbumen (white of egg) to the tissue developed within the nucleus (fig. 610, N), and gave that of vitellus (yolk of egg) to the tissue developed in the embryonic sac (s.z). Fertilization is announced by the appearance of a body (fig. 716) destined to form the embryo, suspended from or near the top of the embryonic sac (s.e). At first it consists of a vesicle (v.e), named embryonic vesicle, filled with a granular mat- ter, in which is formed first one cell, then others, each of which bears a cytoblast on its wall. The upper and slender portion of this vesicle (fig. 717) is the suspensor; in the lower and swollen portion the embryo is developed; the vesicle and its suspensor , soon disappear, when the embryo develops, according 717. Dicotyledonous em-
to whether it is monocotyledonous or dicotyledonous, “hryo, in different stages of development
2 3
716. Pol A . « eB Fertitized ovule, out @8 we have already shown, and increases within the inthe ovule (mag).
vertically (ma) gavity of the ovule, which it invades by absorbing
the albumen. If the albumen has solidified before the growth of the embryo, the latter remains small and takes up less room; and the absorption of the albumen is then delayed till the period of germination. The ovule is not always provided with two coats; sometimes the inner coat alone (secundine) is developed (Walnut, fig. 718); in others the nucleus remains naked (Santalacee, Mistleto, fig. 712). It is important to understand the changes the ovule may undergo before fertilization ; changes due to unequal development altering the relative posi- tions of its different parts. In theory, the hilum and chalaza correspond, and occupy the base of the ovule, the micropyle being at the top or opposite end. If the ovule develops uniformly, the arrangement is not disturbed, and the ovule is straight or orthotropous (ov. orthotropum, fig. 716), and the embryo will also be straight. In this case the position of the radicle answers to that of the micropyle, i.e. opposite the hilum and chalaza, and the embryo is said to be antitropous (ov. antitropus, Nettle, fig. 578).
When the ovule develops unequally, one of two things may happen: 1, the chalaza (Ch, fig. 718) may be removed from the hilum towards the position occupied by the top of the* ovule; which top, by a reverse movement, may be turned towards the hilum; the axis of the ovule thus making a half turn upon itself, like a compass- needle turning from the north to the south pole. In this case the hilum not having been displaced, the vascular bundle which connects
ch,
2 Fae
| PLES n 718. Dandelion. Anatropous ovule 719, 720, 721. 722, 723. Vertical section cut vertically (mag.). Chelidonium.—Anatropous ovule in different stages of development (mag.). of fig. 722.
it with the chalaza is forced to follow the latter in its revolution, and form a more or less projecting cord (8) in the thickness of the primine, named the raphe; the ovule is then reversed or anatropous (ov. anatropum, figs. 719 to 728). Here the embryo
FUNDAMENTAL ORGANS. 137
will be straight, as in the Nettle, but the chalaza will be the antipodes of the hilum, the micropyle nearly touching the latter, andthe radicle corresponding to the base of the ovule; such an embryo is called homotropous (ov. homotropus). ‘here are many examples of this (Sage, fig. 579; Chicory, fic. 580).
2. When the hilum and chalaza (figs. 724 ch, 725) are inseparable, and one side of the primine (p) is more developed than the opposite side, the one lengthens while the other remains stationary; the resistance of the stationary side causes the lengthening side to turn around the centre of resistance ; the ovule (n) thus bent back upon itself is said to be campylotropous (ov. campylotropum).
724, Wallflower.
e 725. Wallfi if Campylotropous ove Here the embryo will follow the curvature of Campylotropous ovule, cut anne the ovule, and the micropyle and chalaza (ch) Fea Sees
being both close to the hilum, the radicle and cotyledonary ends will be only separated by the hilum, and the embryo is called amphitropous. The Wallflower (figs. 724, 725) and the Mallow (figs. 726-730) are well-marked instances of the curved ovule and amphitropous embryo.
To these three types (orthotropous, anatropous, and campylotropous) all ovules properly belong; but there are many cases of intermediate types, which it is neces- sary to take into account. In one case which, although very rare, runs through the whole family of Primmulacew, and occurs in Vinca, one side of the ovule develops
726. 727, 728. 729, 730. Vertical section Mallow.—Campylotropous ovule in various stages of development (mag.). of fig. 729.
enormously, while the other gradually atrophies; this action continues after
fertilization, and the micropyle, approaching the hilum more and more, ceases to ’ correspond to the radicle, which may hence be variable in direction ; most commonly the axis of the embryo becomes parallel to the hilum, and the embryo is called heterotropous (ov. heterotropus, Plantain, fig. 592; Asparagus, fig. 594).
When the seed is mature, it becomes difficult to distinguish in its coats (testa and endopleura) the primine, secundine, tercine (nucleus), and quintine (embry- onic sac), which all enter into its composition. The testa evidently represents the primine; and, as the raphe has pursued its course between it and the secundine, this latter must be represented by the endopleura ; but the nucleus and embryonic sac are either pushed back by the embryo, and reduced to membranes lining the inner wall of the secundine, or they completely disappear; the secundine itself may indeed disap- pear, and the embryonic sac alone remain with or without the nucleus. Lastly, these
138 ANATOMY.
membranes may be united and confounded, so as to become indistinct. The primine therefore cannot be identified with the testa, except in cases when the latter can be cleanly removed, exposing the raphe between it and the endopleura; and then the endopleura is obviously formed by the secundine, with or without the tercine and quintine, as may be easily seen in the Orange.
The three typical modifications in the positions of the parts of the ovule being known, we will indicate the corresponding portions of the embryo in the seed :—
First Typr.—Ovule straight (orthotropous), and consequently embryo antitropous ; —the seed may be: 1, erect (radicle superior) ; 2, pendulous (radicle inferior) ; 3, hori- zontal-parietal (radicle centrifugal) ; 4, horizontal-awile (radicle centrifugal).
Seconp Trpr.—Ovule reversed (anatropous), and embryo homotropous ;—the seed may be: 1, erect (radicle inferior); 2, pendulous (radicle superior); 3, horizontal- parietal (radicle centrifugal); 4, horizontal-aaile (radicle centripetal).
Tuirp Typr.—Ovule curved (campylotropous), and embryo amphitropous; if the embryo is not much curved, the radicle is inferior, superior, centripetal, or centri- fugal, according to the position of the micropyle ; if neither extremity of the embryo is turned towards the hilum, owing to the unequal growth of the coats, it is said to be heterotropous; it may then be either straight, curved, or flexuous, and the radicle is inferior, superior, centripetal, centrifugal, or vague.
ACCESSORY, ORGANS.
To complete the anatomy of the elementary and fundamental organs, we must describe that of certain modifications of the cellular tissue: these are prickles, hairs, glands, and lenticels.
Prickles.—These are composed of a cellular tissue analogous to that of the bark; they must not be confounded with spines, which are fibro-vascular, and are merely transformed organs, whose nature is indicated by their position; i.e. they are aborted branches (Blackthorn, fig. 51), hardened stipules (Robinia, fig. 114), petioles of pinnate leaves become spiny after the fall of the leaflets (Astragalus Tragacantha), leaves of which the nerves have lengthened into spiny points, to the destruction of the parenchyma (Berberis, fig. 94); cushions, which elongate greatly, and become pungent (Gooseberry, fig. 95). Prickles, on the contrary, are dispersed without order on the stem and leaves, and even on the corolla, and are thickened, hardened, and
pungent hairs. When young, they exactly resemble hairs, of which we are about to speak, and it is only when older that they thicken, lengthen, and harden; they occur on the Rose (fig. 50) in every stage of its growth. eat a ‘ Hairs.—Cellular organs, which principally occur on branches, ae ‘ : 984. étage: petioles, and the nerves and under surface of leaves, especially young Sepueciet Ones 5 they are lengthened epidermal cells, covered by cuticle, like those cells which do not lengthen. Hairs are unicellular, when formed of one elongated, vertical, oblique, or horizontal cell, which may remain simple
ACCESSORY ORGANS. 139
(fig. 781), or branch in a fork (fig. 732), trident, star (fig. 733), &. Some branch in stages, and resemble superimposed whorls (fig. 734). Chambered, a or jointed hairs are composed of cells joined end to end, and forming simple beads (figs. 735, 786) or branches; sometimes a bundle of hairs radiates horizontally from a common centre, and, being united
732. Whitlow:
gra3s. Bifur- i “cated one- 733, Alyssum, 735. Tradescantia. 736. Mirabilis. 737. Eleagnus. 734. Alternanthera. celled hair Starred one-celled Chambered hair Hair resembling Radiated hair Branched hair (mag.). hair (mag.). (mag.). anecklace(mag.). (mag.). (mag.).
by the cuticle, resembles the rays of the sun (fig. 737). The small brown scales observable on ferns are considered as scarious hairs.
Glands.—These are organs of secretion, i.e. they extract a peculiar liquid from the materials with which they come in contact; they are entirely cellular; the cells of some glands project, and are called slantidiee hairs, which only differ from ordinary hairs by the liquid they contain ; some are swollen at the tip; most are unicellular, as those on the calyx of the Sage (fig. 738), and on the velvety palate of the Snapdragon (fig. 739).
The stinging hairs of the Nettle (fig. 740) are formed of a single conical cell, of which the base is swollen into a bulb, and surrounded by a group of epidermal cells; the top is lightly bent, and it is the fragile tip of this hair which, breaking in the skin which it has penetrated, intro- \ duces the venomous juice contained in the cell. The sting- ing hairs of the |
Wigandia have a lanceolate tip. (fig. ee 741) . Glandular hairs 738. Sage. 739, Snapdragon. _ 740. Nettle. 742, Snapdragon. 741. Wigandia. Glandular Glandular one- Stinging one-celled Glandular Stinging hair may be chambered, one-celled hair celled hairs hair, bent chambered hair with lanceolate (mag.). (mag.). at the top (mag.). (mag.). point (mag.).
when the terminal cell alone is glandular, as in the calyx of the Snapdragon (fig. 742); or there may be several superimposed cells; but it is invariably the upper ones alone which secrete. Peltate hairs are composed of one cell lying horizontally on the leaf, and adhering by its centre to the epidermis, by means of a gland which forms its base (Malpighia).
True glands differ from glandular hairs only in projecting slightly or not at all
140 ANATOMY.
above the epidermis ; they pass insensibly into each other, as in glandular roses. The superficial glands covering the bracts and flowers of the Hop (fig. 743) are simple vesicles (fig. 744) containing a liquid, and a resinous principle called by chemists lupuline; these vesicles burst and soon disappear, when the resinous principle remains in the form of powder. Sometimes the glands are sunk in the thickness of the bark, but they are always near the epidermis; such are the glands called vesicular of the leaves of St. John’s Wort and Myrtle, and of the bark of the Orange, which contain a volatile oil (fig. 745).
We have already described the necturiferous glands or nectaries, which secrete a sweet liquid (p. 74).
The cavities called reservoirs of proper juice, in which gums, resins, &c., are elaborated and accumulated, are lined with peculiar cells; they are Wi} analogous to the vesicular glands, but more deeply immersed in the tissue. {\\}
Lenticels, formerly called lenticular glands, are not glandular; they
PD, a PSS G3 Qo6SS = TOUS CCS PEs0NIS_S"O
745. Orange. 2 744. Hop. Vertical section of a fragment of rind, 743. Hop. Superficial glands containing showing the _ 746. Willow. ® flower (mag.). lupuline (mag.). reservoirs (R) of volatile oil (mag.). Lenticels,
are prominences on the surface of the stem (fig. 746, 1), produced by excrescences of the endopleura which have pierced the bark. Adventitious roots often spring from lenticels; but they also spring from many other points; which invalidates the opinion of De Candolle, who regarded lenticels as the buds of aérial roots.
ANATOMY OF ACOTYLEDONS.
Stem.—The stems of Ferns more nearly resemble those of cotyledonous plants than do those of any other acotyledonous order. A transverse section of a Tree-fern stem (fig. 747) shows fibro-vascular bundles (f, v) of various forms, disposed in a more or less irregular circle, which surrounds a yellowish central disk (m), and is itself sur- rounded by a zone of the same colour (p); this disk and zone are cellular, and communicate by larger or smaller passages between the bundles. The outermost blackish zone is an envelope formed subsequently to the epidermis, of the bases of the fronds. A transverse section of the bases
747. Cyathea. : 5 ‘Transverse section of thestem. of these fronds displays a structure analogous to that of the
stem, on which their bases, when detached, leave remarkable scars. The same
ANATOMY OF ACOTYLEDONS. 141
structure and scars characterize the stems of the herbaceous ferns of Europe (figs. 748, 749). The fibro-vascular bundles of ferns, whether exotic or indigenous, con- sist of a pale portion (fig. 747, v), formed of annular and radiating prismatic (scalariform) vessels, surrounded by a very narrow black zone (f), formed of woody fibres. Trachez are invariably wanting.
A few other acotyledonous families con- tain fibro-vascular bundles in their stem; in Mosses and Hepatice the stem is com- posed of elongated cells, which sometimes 4)\\ become fibres ; the tissues of Lichens, Fungi, Alge, &c., are entirely cellular.
Root.—The roots of the higher acoty- ledons, such as ferns, present the same
748. Male Fern. structure as the stems; i.e. bundles of fibres paces Transverse econ ofthe and vessels, surrounded by cellular tissue; Rhizome showing the scars (0)
tees of the old fronds. these roots are always adventitious and often
aérial. In the lower acotyledons they are formed of cells which reach the ground, and then lengthen and bury themselves.
Leaves.—The leaves of acotyledons present the same structure as their stems ; in ferns, we find radiating prismatic vessels and black fibres; in Marsileacee, the nerves are numerous; in Lycopodiacee, the leaf is a cellular plate traversed by a single fibro-vascular bundle; in Mosses and Hepatic, the nerves are represented by elongated cells; in the lower acotyledons, the leaves and stem are represented by a frond entirely composed of cellular tissue.
Reproductive Organs.—Antheridia are little sacs, at first perfectly closed, then opening at a certain period at one point of their surface, and emitting by this opening a mass of corpuscules, usually cohering by means of a mucilaginous liquid ; these organs are considered analogous to anthers ; we shall explain their nature in the description of the Orders.
Spores are little membranous sacs, full of liquid, which germinate by lengthening at some undetermined point of their circumference, and develop into a little plant similar to that which produced them. Spores are formed in particular cavities, called sporangia ; they are the analogues of seeds, with regard to their functions, but they possess neither coats, caulicle, radicle, plumule, nor cotyledons; they are developed freely in the sporangium, and never. adhere to its walls, as the seeds of cotyledons adhere to their placenta. The sporangium, which fulfils the functions of a carpel, has neither style, stigma, nor ovarian cavity; it is filled with a con- tinuous cellular mass, in the midst of which are certain isolated cells, destined to reproduce the plant. We shall explain the spores and sporangia when describing the characters of the Orders.
ELEMENTS OF VEGETABLE PHYSIOLOGY.
FOOD OF VEGETABLES.
The food necessary for the development of the plant is drawn from the soil by the root, and is absorbed by means of the spungioles which terminate the root-fibres, and which are composed of a renewable cellular tissue having no epidermis.
The substances drawn from the soil are, carbonic acid, ammonia, and alkaline and earthy salts dissolved in water. Carbonic acid comes: 1, from the rain, which has dissolved it in passing through the atmosphere ; 2, from the slow decomposition of humus or mould, the carbon of which combines with the oxygen of the air, which the water holds in solution. The ammonia comes: 1, from rain during storms, when, by the influence of electricity, it is formed from the nitrate of ammonia; 2, from the putrefaction of vegetable or animal matter, at the commence- ment of which azote and hydrogen combine. This decomposition is aided by adding chalk to cultivated soil; for chalk, as Boussingault has proved, attacks insoluble azotized matters, and favours the formation of ammonia. The alkaline and earthy salts, and notably the sulphates, and phosphate of lime are derived from the soil; the sulphates are decomposed by the ammonia, which substitutes itself as their base, and forms a sulphate of ammonia, which, being soluble in water, and containing azote, hydrogen, sulphur, and oxygen, is eminently adapted for the nourishment of plants. Phosphate of lime, which is insoluble in pure water, is soluble in water containing either an ammoniacal salt or carbonic acid only, as is the case with rain. The water which holds in solution these different inorganic substances is a colourless liquid, which rises by the vessels into the root, stem, and leaves, fills the cells and their interstices, in which, during life, are formed the organic matters which are to be deposited in the tissue of the vegetable, or to assist in its growth.
The above-mentioned inorganic substances are all binary compounds, which sometimes remain, isolated, sometimes enter into combination with one another. But the organized substances which are found in the plant are the results of more com- plicated combinations ; we have already spoken of cellulose and starch, allied to which is a third substance named dextrine, which does not turn blue with iodine, and which is soluble in water; its chemical composition is exactly the same as that of cellulose and starch, which are ternary bodies, composed of carbon, together with
FOOD OF VEGETABLES. 143
hydrogen and oxygen in the same proportions as water. These three bodies, formed from the same elements in similar proportions, are called isomerous bodies; the difference between them consists entirely in the manner in which their molecules are grouped; it is therefore simply necessary to derange these molecules to convert dextrine, cellulose, and starch into each other.
The sugar yielded by the Sugar-cane, Beetroot, and many other vegetables is also a ternary compound very similar to the preceding ones, containing one molecule more of water than starch, dextrine, and cellulose contain.
Glucose or grape-sugar only differs from cane-sugar in containing three molecules more of water. Thus starch or dextrine, with an additional molecule of water, becomes cane-sugar; ard grape-sugar from which three molecules of water are abstracted becomes cane-sugar.
Organic acids, such as acetic acid, which is found in the sap of plants, and forms in sour wine, pectic acid in the gooseberry, tartaric acid in grapes, malic acid in apples, cifric acid in the lemon and other fruits, gallic acid in oak-galls and bark, &c., are ternary compounds which contain carbon and the elements of water (oxygen and hydrogen), plus a certain quantity of oxygen. Ovtls, essences, resins, chromule or chlorophyll, are ternary compounds, formed by the combination of carbon with the elements of water, plus a certain quantity of hydrogen.
Besides these, vegetables contain, especially in their bark, quaternary compounds of carbon, hydrogen, oxygen, and nitrogen; these crystallize, and are always found in union with an organic acid which forms a salt with them, whence their name of vegetable alkalies.
The Poppy contains morphine, narcotine, &c.; the Nua vomica, strychnine; the genus Cinchona, quinine, cinchonine, and cusconine. Experience has proved that the poisonous and medicinal properties of vegetables reside in the organic alkalies.
Other organic substances frequently found in vegetables are still more com- plicated ; for, besides oxygen, hydrogen, carbon, and nitrogen, plants contain sulphur and phosphorus: these are albumen, fibrine, and casein; the proportions of their elements are similar, although their physical properties are different; whence the name of protein by which chemists designate the essential principle of all those substances that are collectively designated albuminous. Protein has been alluded to under the nucleus; it constitutes the nutritious element of vegetables, for without it no blood can be formed, and it is always found in this liquid. I brine isa compound substance, insoluble in water, like cellulose; it may be looked upon as the origin of all the parts of a plant; it always exists in them, and especially in the seeds of cereals. Albumen coagulates with heat like starch; it constitutes nearly all the serum of blood and the white of eggs, and abounds in the juices of plants. Casein, which forms with starch the nutritive part of beans, lentils, and peas, constitutes essentially, in the milk of animals, the nutriment thatthe young receives from its mother. Gluten, which forms the base of leaven or yeast, exists in most seeds, and is composed of the same elements (less the sulphur and phosphorus) as albumen, fibrine, and casein.
The elements of carbonic acid (oxygen and carbon), of ammonia (hydrogen and
Lit VEGETABLE PHYSIOLOGY.
nitrogen), of water (oaygen and hydrogen), and the sulphur of soluble sulphates, supply most of the materials of vegetables. The carbon of carbonic acid by uniting with the elements of water forms celiulose, sugar, gum, starch, &c.; an excess of oxygen produces vegetable acids (malic, citric, acetic, gallic, &c.); an excess of hydrogen produces chlorophyll, oils, resins; the azote of ammonia, added to the elements of water and of carbonic acid, gives rise to vegetable alkalies (quinine, morphine, &c.) ; finally, sulphur and phosphorus, combined with azote, oxygen, hydrogen, and carbon, form three organic substances of similar composition, namely, fibrine, albumen, and casein; these supply the animal kingdom with essentially nutritious elements; as stated above, they are always found in the blood, united with other substances, and notably with a certain quantity of phosphate of lime, a salt which constitutes the solid part of bones.
Humus or mould is the name given to the black carbonaceous matter which results from the decomposition of organic substances; vegetable mould is nothing but cellulose, which burns slowly under the influence of the oxygen of the atmosphere, and changes into carbonic acid, which, dissolving in the water of the soil, passes into the substance of the vegetable. The decomposition of the mould is assisted by mineral alkalies (potash, soda, chalk, magnesia), which induce the formation of carbonic acid, and form with it soluble carbonates, absorbed by the roots; then, under the influence of these same alkalies, the water and carbonic acid decompose, and vegetable acids are formed, more or less oxygenized, with which they combine ; finally, these acids change, and become sugar, starch, or cellulose.
Thus, vegetable acids are indispensable to the existence of plants, and their formation depends: 1, on the water and carbonic acid which combine to form them ; 2, on the mineral alkalies which induce this combination. Now these alkaline bases, which play so important a part in vegetation, reside in hard or soft rocks, named feldspar, mica, granite, gneiss, basalt, the elements of which are silica, alumina, potash, magnesia, lime, &c.; these bases are liberated by the disintegration or decomposition of the rocks, of which the débris, more or less changed, constitute arable soil. The rocks are disintegrated by the water which, having penetrated them, expands in passing to the state of ice, and thus overcomes the cohesion of their elements. These elements are then dissolved by water, either pure, or containing oxygen, or loaded with carbonic acid; it is thus that the aluminous and alkaline silicates are disintegrated and dissolved, previous to forming argillaceous soils.
Alkalies, and especially potash, when mixed with soil, are rendered soluble by the addition of sulphate of lime, as Dehérain has proved. Since the sulphate of lime changes the salts of potash into sulphate of potash, it has been supposed that the greater solubility of potash after being thus treated is attributable to this trans- formation; this hypothesis has not yet been practically proved, and we do not know whether the sulphate acts chemically on the potash, or whether its effects are purely physical, the object being to liquefy the soluble salts, to preserve them from the ab- sorbent action of the earth, and to facilitate their absorption by the roots of the plant. But, whatever be the explanation, this property of sulphate of lime proves the advantage of adding it to the soil in which leguminous fodders are cultivated (Lrefoil, Lucerne,
NUTRITION OF VEGETABLES. 145
Sainfoin), of which the ashes are rich in potash; while, on the contrary, the addition of carbonate of lime, which induces the formation of ammonia, is very usefully employed in the cultivation of cereals, for which azotized manures are necessary.
Silica is useful, because, being powdery and insoluble, it admits air and mois- ture, alumina, because it retains moisture, around the roots; lime, because, under the influence of water acidified by carbonic acid, it replaces the alkaline bases of the silicates ; hence the importance of marl, which is a mixture of clay and lime. If the soil is composed of pure silica or of pure chalk, it is absolutely sterile ; if it is wholly of clay, the roots cannot penetrate it. The best soil is that in which clay is mixed with carbonate of lime and sand (silica), in such proportions that air and moisture readily permeate it.
Tillage improves the soil by breaking it up, and multiplying the surfaces which ought to be in contact with carbonic acid, the ammonia of the rain, and the oxygen of the air, so that the débris of the rocks may be rendered soluble, and form arable land. The period of fallow is that during which the soil is left to atmospheric influences. While the land is thus left fallow as a preparation for certain crops, it may be occupied by some other plant which does not rob the soil of the materials required for such crops; this explains the theory of the rotation of crops.
NUTRITION OF VEGETABLES.
Absorption.—The roots are the principal organs of absorption ; they pump up the liquid into which they are plunged, by means of their permeable cells. The upward movement of the sap is-explained by a recent discovery in physics :—if a tube closed below by a porous membrane, and filled with a dense liquid, is plunged into a less dense coloured liquid, there is soon a tendency to establish an equilibrium of density, and the dense liquid in the tube becomes coloured by the addition of the less dense liquid outside it, and the two liquids stand at different heights; that in the plunged tube rises above its level, and only stops rising when its density is no longer greater than that in the outer tube. But to produce this equilibrium, the exterior liquid must receive a certain quantity of that within; thus there is a double current esta- blished through the porous membrane; the one from without inwards, called endos- mose; the other, less in degree, from within outwards, called exosmose.. This action accompanies the absorption of fluid by the roots; the damp soil contains water laden with ammonia, carbonic acid, and different salts ; the roots, as well as the stem, are composed of a series of superimposed cells, some of which are filled with a dense juice, and others with vessels in which the liquid can easily rise by capillary action ; the spongioles which terminate the root-fibres having no epidermis, are very permeable, the water of the soil penetrates them, the juice which they contain is diluted by this water, and to establish equilibrium the sap rises from cell to cell to the top of the plant.
Circulation.— When the water of the soil, laden with the carbonic acid, ammonia, and mineral matters dissolved in it, has penetrated the plant, it takes the name of
I
146 VEGETABLE PHYSIOLOGY
ascending sap; this sap thickens as it ascends, in proportion as it dilutes and dissolves the materials in the cells; but to the motive force of the endosmose and capillary action is added another not less powerful: this is the attraction exerted from above by the buds, which draw up the food necessary to their development, and by the already formed leaves, from the surface of which copious evaporation is carried on. The empty spaces resulting from this evaporation and from the substance assimilated by the buds, are filled by the sap in the parts immediately below; these repair their losses in their turn, and this action is continued from above down to the roots, for which the soil is the reservoir.
The buds are the first organs of the vegetable which awake in spring from their winter torpor; when they begin to swell, the resulting movement of the sap stimulates the roots, which recommence their functions; from this time the ascending current, assisted by the endosmose, is established through the swollen tissues of the thickened | materials deposited the preceding year. Nevertheless, although it is the buds which give the roots the signal to reeommence their work, the work of the roots is carried on independently of the influence of the buds; for these remain closed long after the sap has begun to rise with remarkable force and abundance. If at the period of the spring sap an incision is made in a stem, a stream of sap flows from it, and the proof that neither the buds nor the leaves are the cause of this phenomenon is that it occurs just the same on a stem deprived of buds and leaves. An example of this is seen in the tears of the vine, which flow from the stem when the plant is pruned, and even when it is cut almost to the ground; but as the buds lengthen, and as the branches resulting from their elongation become covered with leaves, the suction of the young branch and the evaporation from the surface of the leaves become active forces, which join those of the endosmose and capillary action to assist the ascension of the sap.
When the branches are developed and consolidated, the movement of the sap slackens, but without ceasing ; its only object now is to provide for the daily require- ments of the plant, and to prepare materials for the vegetation of the following year. When the spring rise of sap has taken place early, these materials are prepared before autumn, and then the August sap is produced, which represents a second spring.
In the autumn, the tissues, more and more solidified, dry up; the leaves, of which the canals become obstructed by a continual efflux of materials, cease to vege- tate, and fall; evaporation is thenceforth arrested, and with it the movement of the sap ; and finally, life is suspended for several months.
The ascent of the sap does not always take place in the same manner ; in spring it rises across all the woody tissues ; in old branches, across the sap-wood only. Later, most of the vessels are empty except of gases; it is then by the cellular tissue that the sap rises to support the vegetation.
When the sap, laden with the materials that it has dissolved in fis ascending and diverging march, has reached the young branches, it penetrates their cortical pith and the parenchyma of the leaves; there it finds itself in contact with the air which has penetrated by the stomata into the intercellular spaces; then it under- goes important modifications, and loses a large portion of its water, which evaporates
NUTRITION OF VEGETABLES. 147
on the outside. The cells of the green parts of the bark and leaves fill with chloro- phyll. The latex of the laticiferous vessels becomes charged with coloured granules, and the sap, thickened and enriched with new principles, descends from the leaves along the inner surface of the bark towards the roots. This descending movement is easily proved ; it is sufficient to prune the bark of a young branch to see the sap, if it is coloured, ooze from the upper lip of the incision and not from the lower. If the stem be tightly corded, after some time the bark swells, and forms a cushion above the ligament, while the stem below will preserve its original diameter. For this reason the elaborated sap is also called descending sap.
The elaborated sap furnishes the cambium, a gelatinous fluid which permeates the cellular zone, and in which are formed the elementary organs which combine to produce growth in the vegetable.
In dicotyledonous stems, the cambium is principally deposited between the woody and cortical systems, within the layer of laticiferous vessels and the fibres of the liber, in contact with which the descending sap flows. The young buds springing from the axil of a leaf are placed in the direction of the flow of latex from that leaf, and which, accumulating at the base of the petiole, elaborates there the elements of cambium.
In monocotyledonous stems, the fibres analogous to the liber and the vessels of the latex, which each fibro-vascular bundle contains, furnish an elaborated sap, which deposits cambium in heaps dispersed through the stem; so that their terminal bud profits by the sap elaborated by the leaves of the preceding bud.
Finally, rain, containing the materials for the food of the vegetable, is absorbed by the tips of the roots, rises in the stem, crosses the wood system, reaches the parenchyma of the leaves and the cellular tissue of the bark, where it undergoes the action of the air, becomes elaborated sap, descends through the bark, deposits a zone of cambium between the liber and alburnum, and arrives at the tips of the roots, whence it started; thus establishing a true circulation.
Oyclosis is a peculiar circulation which Schultz has discovered in the laticiferous vessels; he observed that the coloured granules flow in sinuous tracks, being carried by the latex currents in various directions along the courses of the anastomosing laticiferous vessels.
Physiologists have proposed different theories to account for the propelling force which puts the latex in motion; but Mohl has shown that this motion is not a vital phenomenon, but that it always arises, either from a rent in the tissue, whence the latex necessarily escapes, or from a mechanical pressure on the tissue, which sets the latex in motion; as also that this motion soon ceases.
But if cyclosis is an obscure and doubtful phenomenon, this is not the case with the intercellular circulation (rotation), which can be observed in the septate hairs of certain plants (Tradescantia), and especially in the cells of certain aquatics (as Chara). Chara is a leafless, frondless acotyledon; its internodes, whether isolated or in bundles, consist of cylindrical cells placed end to end; each internode pro- duces at its top a whorl of cells similar to itself, which speedily become similarly septate. If one of these cells be placed under a microscope, and cleared from the
L2
148 VEGETABLE PHYSIOLOGY.
calcareous crust which often envelops it like a bark, numerous granules are seen floating in a transparent liquid within the cell, and forming a current which rises along one of the lateral walls, then flows horizontally along the upper wall, then descends along the other lateral wall, and becomes again horizontal along the lower wall of the cell. It is this intracellular motion which has been called rotation, a very inappropriate term, for which it would be better to substitute that of cyclosis (abolished by Hugo Mohl), which expresses much more exactly the circular move- ment of the sap in the cell.
Respiration.—The carbon of plants is derived from the carbonic acid contained in the air; the roots absorb it with the water of the soil which holds it in solution ; whilst the carbon of the air enters the leaves through their stomata. Many experiments prove that the leaves and green parts exclusively possess the power of decomposing carbonic acid, thus separating the oxygen, and restoring it to the atmosphere; they also decompose water and retain the hydrogen; this power is only exercised under the influence of sunlight. Now animals are constantly burning carbon by means of the oxygen of the air, and exhaling carbonic acid, in which operation they consume an enormous quantity of oxygen; but plants, by their respiration, restore the balance, for they provide an inexhaustible store of pure oxygen, and incessantly repair the loss which the atmosphere has sustained through the respiration of animals.
The power possessed by leaves of decomposing carbonic acid ceases at night or in darkness ; then the carbonic acid, absorbed by the roots with the water of the soil, enters the stem, and remains dissolved in the sap with which the plant is impregnated ; soon this water evaporates through the leaves, and carries off the carbonic acid which it held in solution.
The green parts of plants absorb oxygen during the night by a chemical process, which tends to produce a change in the materials contained in their tissues. To blanch plants, they must be placed under the same conditions as the green parts of vegetables are during the night, namely, in continuous darkness; the carbonic acid is then not assimilated, the green chlorophyll is not formed, and their tissues con- tain an excess of water; and the horticulturist is thus enabled to expel the bitter principle from stems or leaves.
This exclusive property of the green parts is perhaps due to their having absorbed the chemical rays of the solar light, which rays may aid in the decom- position of carbonic acid in the chlorophyll.
Respiration, which is the reciprocal action of the sap upon the air, and of the air upon the sap, is carried on in the intercellular spaces (lacune) beneath the stomata, where the air comes into contact with the parenchyma. Submerged plants, which have no epidermis, and whose parenchyma is hence exposed to the fluid, decompose the carbonic acid which the water always contains, under the influence of light transmitted through the water; they fix the carbon and reject the oxygen, which remains in solution, and supports the life of aquatic animals. Here, as in the air, the Animal and Vegetable Kingdoms reciprocate only under the stimulus of light; and if the water be too deep, the plant becomes pale and etiolated.
NUTRITION OF VEGETABLES. 149
Besides the elaboration of sap by the green tissues, other truly respiratory processes are carried on in the plant for the purposes of assimilation : thus, when the seed germinates, it absorbs oxygen and liberates carbonic acid; a process analogous to the respiratory in animals, and whichis continued until the first leaves of the embryo are developed. Similar respiratory processes accompany flowering ; the petals and stamens absorb, by day as well as by night, much oxygen, and emit much carbonic acid ; hence the noxious quality of the air in a room full of plants ; which is greatly increased by the exhalation of carburetted hydrogen, contributed by the volatile oils to which the perfume of the corolla is due.
Evaporation is a phenomenon analogous to the pulmonary perspiration of animals, and should be treated of after respiration. Evaporation is one of the most active agents in the ascent of the sap; it goes on through all the pores on the surface of the green parts, but especially through the stomata; increasing or diminishing as the surrounding air is drier or moister.
Leaves possess in a slight degree only the power of absorbing the watery vapour in the air; and though certain uprooted plants remain fresh for some time, this is due to their losing little by evaporation. So, too, leaves floating with their lower surface on the water do not wither, not because they absorb water, but because their stomata being stopped up, evaporation is arrested.
Excretions.—A plant, after being nourished by the materials of the elaborated sap, rejects by its leaves, glands, bark, and especially by its root, all useless or noxious matters. Thus, to express in a few words the nutritive functions of its life, a vegetable may be said to absorb, breathe, assimilate, perspire, and excrete.
Direction of the Axis.—The stem tends always to ascend, and the root as uniformly to descend, and even in underground stems the tip of the rhizome always turns upwards. In the Mistleto, a parasite, the seed, fixed to the branch of a tree, germinates on the bark, and always directs its radicle towards the centre of the ‘branch, and its plumule in the opposite direction ; here the tree takes the place of the soil, and the root obeys a centripetal, the stem a centrifugal force.
Attempts have been made to elude this general law of the direction of axes, by reversing the seeds of young plants, when the root bends round to the earth, and the stem turns upwards. A box of damp earth has been so suspended that seeds could be planted on the lower surface of the earth, the soil being above, air and light below; still the stems rose into the earth, the roots descended into the air.
Movements of Leaves and Flowers.—Leaves constantly direct their inner surface towards the sky, and their outer towards the earth; if this direction is reversed by twisting the base of the petiole, the leaf constantly tends to turn round in spite of all obstacles, and if these obstacles be insuperable, it gradually dies; if the branch be reversed artificially, the petiole twists; if the reversion is natural, as in weeping trees, the torsion of the petiole is spontaneous, and the inner surface turns towards the sky; if, finally, a leaf be so suspended that its blade is horizontal and its inner surface is turned downwards, the blade speedily turns round, and resumes its normal position. This instinct of the leaf depends neither on air nor on light, for it is displayed in water and in darkness. But with many species, the state of the
150 VEGETABLE PHYSIOLOGY.
atmosphere, whether gloomy or bright, dry or moist, hot or cold, gives rise to singular movements in leaves and flowers. Thus, during the night the leaflets of the Bean and of Trefoils rise; those of the Liquorice and of Robinias hang vertically, This phenomenon has been called the sleep of plants; and to prove that this sleeping and waking depends on the absence and presence of light, plants have been. caused to sleep at mid-day, by placing them in the dark; whilst others have been wakened at night by a strong artificial light.
There are various exotic plants, which, waking by day and sleeping by night in their native country, retain in our houses the habits of their climate, which being the reverse of ours, they sleep during our day, and wake when the sun has sunk below our horizon. Tropical plants wake and sleep with us as if we had a perpetual equinox.! Certain plants exhibit movements induced by accidental external stimuli; such is the Sensitive Plant (Mimosa pudica). Its periods for sleeping and waking do not precisely coincide with our night and day, its waking periods being subject to vicissitudes depending on the slightest causes: a gentle shake, a breath of wind, the passage of a storm-cloud, the falling of a shadow, offensive vapours, the most delicate touch, cause the leaflets to droop suddenly, and closely overlap each other along the petiole, which then droops also; but soon after, if the cause be removed, the plant recovers from this sort of fait, all its parts revive and resume their first position.
Venus’ Fly- trap (Dionea muscipula) is a small North American herb, whose excitability is fatal to the insects which approach it; its leaves terminate in two rounded plates, joined by a hinge like the boards of a book, and fringed with marginal bristles; on their upper surface are two or three little glands which distil a liquid attractive to insects‘y when a fly touches these, the two plates close sharply and seize the insect, whose efforts to escape increase the irritation of the plant, which finally crushes it ; when the insect is plies ai dang all 2 all movement has ceaged, th the plates expand again, and await a fresh viet!” Theke e’ phenomena: which are the effect of excitement, are not so exceptional as might be supposed; many plants of our climate offer analogous though much less remarkable examples.
The opening of some flowers is due to the stimulus of light: most open by day, though some by night, as the Marvel of Peru (Mirabilis longiflora and Jalapa) ; others open and close at various hours, and the hour of the day may be ascertained by watching their habits. Linnzus arranged his floral clock in accordance with these periodical changes; but such a clock, in our variable climate, is often too slow or too fast; it can only be correct in the torrid zone, where there are but few atmospheric changes.
The heat and moisture of the atmosphere also influence the daily motions of flowers: certain species foretell rain by closing in the middle of the day, or by remaining open in the evening, or by not opening in the morning. Attempts have been made to construct a floral barometer from these observations, but its perform- ances are far more irregular than those of the floral clock.
1 These statements are opposed to all the established phenomena of plant-life, as known to English observers.—Ep,
151
PHENOMENA OF REPRODUCTION,
Fertilization —Under Organography, the fertilizing action of the pollen on the ovules was alluded to, but not explained; we shall now analyse some details of this wonderful process, the most important of all departments of Vegetable Physiology.
The ancients had confused ideas as to the nature of the stamens; the botanists who wrote after the Renaissance hazarded some vague conjectures on this subject ; and it was only towards the end of the seventeenth century that their true functions were assigned with precision to the pistil and stamen. Tournefort rejected the fact of fertilization, and persisted in considering the stamens as organs of excretion. After his death, the most devoted of his disciples, Sebastian Vaillant, in a discourse delivered in 1716 at the King’s garden, explained the functions of the stamens, and demonstrated incontrovertibly the phenomena of fertilization in plants. Thanks to this discovery, the date of which is known, France claims the honour of the most important discovery which had hitherto been made in Botany. Eight years later, Linneus popularized the doctrine of fertilization by his writings, which were no less remarkable for their learning than for their logical accuracy and poetic charm.
A few examples will suffice to prove the necessity of the pollen to fertilize the ovule. The Date is a dicecious tree, whose fruit is the principal food of certain eastern nations. From time immemorial these have habitually suspended panicles of male flowers on the female plants, when fertilization invariably ensues. These nations, when at war, destroy their enemies’ male Date-trees, and so starve their owners by rendering the female plants sterile.
When the rainfall is excessive at the flowering season of the Vine, the growers say that the vine runs, i.e. that the pistils are abortive ; which is owing to the pollen having been washed away, and fertilization having consequently not been effected. Tn newly-discovered Pacific islands, dicecious Oucurbitacew introduced for the first time have produced female flowers; but there being no males, fertilization has never taken place. Botanists can prevent or produce fertilization by cutting away all or some only of the stigmas of a pistil; in the latter case the ovaries corre- sponding to these stigmas do not produce seed. A pistilliferous Palm cultivated in a hothouse at Berlin had been sterile for eighty years, when some pollen from a staminiferous plant of the same species was sent by post from Carslruhe, by which the Berlin tree was fertilized; it was then left sterile for eighteen years, after which time it was again artificially fertilized, and the operation succeeded as at first. _
Experimenters have employed other means to demonstrate the physiological action of the stamen; they have placed the pollen of one species on the stigma of a different species, belonging to’ the same genus, when individuals have been produced partaking of the nature of both species. Plants thus produced by cross fertilization are termed hybrids; their organs of vegetation are pretty well deve-
*
152 VEGETABLE PHYSIOLOGY.
loped, but those of reproduction are imperfect, and their seeds are unfertile after one or two generations.
Connected with this interesting subject of fertilization is the history of Celebogyne ilicifolia, an Australian Euphorbiaceous shrub, which cannot be omitted here. Its flowers are dicwcious, and for many years female individuals have been cultivated in English Botanic Gardens, which, without the co-operation of stamens (for there is not a single male plant in Europe), have produced seeds which have germinated, and produced in their turn individuals perfectly resembling the mother plant. Here the production of fertile seeds without the intervention of pollen is incontestable. But we do not think that this exceptional phenomenon (which has, however, been almost authentically paralleled by Hemp and Mercurialis, both indigenous dicecious plants) will overturn the admitted doctrine of the fertilization of the ovule by the pollen; and we find no difficulty in admitting that Nature has given to the seeds of certain dicecious plants a power of multiplied reproduction, which may extend to several generations, such as is proved to exist in the case of Aphides. Besides, the force of the anomaly presented by Cwlebogyne cannot be esti- mated atits true value until time shall have shown whether this power is limited or indefinite.
The period of fertilization is that at which the flower exhales its perfume and appears in its full beauty ; the stamens and pistil then exhibit spontaneous motions, which in some species are very remarkable. Thus, in the Berberis, the filaments of the stamens are at first pressed between the two glands of each petal, which as they spread force the filaments to spread also; these soon free themselves under the stimulus of the sun, aided by a slight evaporation which has contracted these and the glands which retained them; when they quickly resume their original bent position and approach the pistil, on which the anthers shed their pollen. This action, which is effected by the solar rays, may be artificially induced, either by gently irritating the filaments, or by shaking the flower; for the least shake or slightest touch releases the stamen. The same irritability is observable in Parie- taria and in Nettles, the filaments of which lie curved back within the calyx, but instantly spring up, if lightly touched; when the anther, which was previously pressed down at the bottom of the flower, is carried up, and sheds a little cloud of pollen. ‘we sheds its pollen with less force but with better aim; it has four or five petals and eight or ten stamens ; on most flowers there is one stamen which, instead of spreading horizontally over one or between two petals, bends over the pistil, against which the filament presses. If patiently watched, the anther will be found to open and emit the pollen; when the stamen, having fulfilled its function, falls back, and another rises to take its place, and so on in succession till all the anthers. have in turn shed their pollen on the pistil. The elasticity of the anthers is not always sufficient to discharge the pollen on the stigma. The conditions under which the pollen is discharged are very various ; in many cases the flower is fertilized before expansion; in many others, the anthers are placed above the pistil, and the pollen is brought directly into contact with the stigma; but it frequently happens that the position of the stamens is unfavourable to their pollen reaching the stigma,
PHENOMENA OF REPRODUCTION. 153
when its transmission ‘is effected by the wind, and especially by insects. ~Butter-— flies, flies, moths, bees, and often very small Coleoptera may be seen at the bottom of flowers, eagerly seeking the honey, and thus becoming useful auxiliaries in the fertilization of the pistil, either by dispersing the pollen with their wings, or by carrying the pollen of one plant on the hairs of their bodies to another plant of the same species. Here we must notice a very interesting series of coincidences : when the anthers open to shed their pollen, the stigma becomes viscous to retain it; nectar is distilled by the glands, and nectar-feeding insects make their appear- ance; lastly, at the same—often very brief—-period, the corolla expands, whose colour and scent must affect the powerful sight of insects and their subtle sense of smell.
Mr. Darwin has recently published, on the fertilization of certain plants, experi- ments which throw a new light on Natural Science, and plainly reveal the marvellous precautions taken by Nature to prevent the degeneration of species. He has en- deavoured to give the rationale of the differences observable in the flowers of Primula. In this genus the same species presents two very remarkable forms: a long-styled, in which the stigma is’ globular and wrinkled, and exactly reaches the mouth of the corolla-tube, far overtopping the anthers, which only reach half-way up the tube. In the other form the style is not half the length of the corolla, and the stigma is de- pressed and soft, but the anthers occupy the upper part of the tube, their pollen is larger, and the capsule contains more seeds than that of long-styled individuals. This dimoxphism between longistyled and brevistyled primroses is constant; the two forms are never met with on the same individual, and the individuals of each form are about equal in number. Mr. Darwin covered with netting plants of both the long- styled and short-styled forms, most of which flowered ; but as neither produced seed, he concluded that insects are necessary to their fertilization. But as, in spite of his utmost vigilance, he never saw any insects approach uncovered primroses during the day, he supposes that they are visited by moths, which find abundant nectar in them. He endeavoured to imitate the action of insects, which, while extracting honey from flowers, are the agents of their fertilization, and his experiments led him to very interesting conclusions. If we introduce into the corolla of a short- styled primrose the trunk of a moth, the pollen of the anthers placed at the mouth of the tube adheres to the base of the trunk, and it may be concluded that this
-pollen will necessarily be deposited on the stigma of the long-styled primrose when the insect visits it. But in this fresh visit, made to the long-styled primrose, the trunk, descending to the bottom of the corolla, finds the pollen of the anthers which are situated there; this pollen adheres to the end of the trunk, and if the insect visits a third flower, which is short-styled, the end of its trunk will touch the stigma placed at the base of the tube, and will deposit the pollen on it. Besides this it may be admitted as very probable that in its visit to the long-styled flower, the insect, in drawing back its trunk, may leave on the stigma a portion of the pollen from the anthers placed lower down, and the flower would be thus fertilized by itself. It is besides nearly certain that the insect, when plunging its trunk into a short-styled corolla, will have rubbed the anthers inserted at the top of the tube,
154 VEGETABLE PHYSIOLOGY.
and deposited on the stigma of the flower a portion of its own pollen. Finally, the corolla of primroses contains many tiny hemipterous insects, of the genus Thrips, which, moving about the flower in all directions, transport from the anthers to the stigma the pollen which adheres to them ; by which means again the plant will be self-fertilized.
In the fertilization of dimorphic species four operations are thus possible :—1, self-fertilization of the long-styled flower; 2, self-fertilization of the short-styled flower ; 3, fertilization of the short- by the long-styled ; and 4, that of the long- by the short-styled: the two first Mr. Darwin calls homomorphic; the two others, hetero- morphic. ;
Mr. Darwin has artificially fertilized flowers in these different ways, by pro- tecting them from insects, and he has found in the wild primrose (Primula veris) and in the Chinese primrose (Primula Sinensis) that heteromorphic unions produce con- siderably more capsules and good seeds than homomorphic unions. Thus prim- roses present two sets of individuals, which, although belonging to the same species, and both possessing stamens and pistils, are mutually dependent on each other for perfect fertilization. Mr. Darwin concludes that Nature, in establishing dimorphism in primroses, and in distributing the two forms in equal numbers of individuals, has evidently had in view the crossing of distinct individuals ; the relative heights of the anthers and stigmas obliging inseets to deposit the pollen of one set on the stigma of the other. Nevertheless it is impossible not to admit that the stigma of the visited flower may receive its own pollen. Now it is a well-known fact, that jf the pollen of several varieties fall on the stigma of one individual, that of one of the varieties is prepotent, and its pollen takes effect to the exclusion of that of all the others. Mr. Darwin thinks that it may be inferred from this that in primroses the heteromorphic pollen, which is known to be the most potent, will overcome the action of the homomorphic pollen whenever the two come into collision; thus, he adds, indicating the efficacy of dimorphism in producing crosses between individuals of the two forms. These two forms, although both bearing stamens and pistils, are in this case truly dicecious; each of them is fertile, though the pollen of each is less potent on its own stigma than on that of the other form.
Mr. Darwin has studied dimorphism in the different species of Linum, and he has instituted on DL. grandiflorwm and perenne a series of experiments which confirm the preceding conclusions.
The scarlet-flowered L. grandiflorum has also the two types of long and short- styled flowers; in the short-styled form the five stigmas diverge, project between the filaments, and rest against the tube formed by the petals. In the long-styled form, on the contrary, the stigmas are erect, and alternate with the anthers. Mr. Darwin selected twelve flowers of two long-styled individuals which he fertilized heteromorphically, i.e. with pollen from the short-styled form; most produced good capsules and seeds; those which were not touched remained absolutely sterile, although their stigmas were covered with a thick layer of their own pollen. He next sought to ascertain the probable cause of this sterility, by placing the pollen of a short-styled flower on the five stigmas of a long-styled flower, and after thirteen
P