The elements of botany embracing organography, histology, vegetable physiology, systematic botany and economic botany ... together with a complete glossary of botanical terms

Front matter

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Preface

THE object in preparing this book has been to present to pupils in our schools and to students generally, in a sufficiently condensed form, a comprehensive view of the Vegetable Kingdom. This includes a general survey of the organs of plants, their structure and functions, of the classification of plants according to their supposed genetic relationship, and, finally, of the uses of plants and the application of botanical knowledge in the various pursuits of life. It is not deemed necessary to apologize for presenting the minute anatomy or histology of plants as seen in the following pages, much less for devoting a separate part of the work to a discussion of the commonest vegetable products found in commerce, as regards their nature, source, and uses. It is believed this new departure will be welcomed by the great mass of intelligent educators of our country, who think this science broad enough and already sufficiently developed to meet the just demand made upon it not only for something disciplinary and pleasurable, but also for something useful. In case of pupils who will afterward pursue collegiate courses of

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vi PREFACE.

instruction, it is believed this book will offer a suitable introduction to extended botanical study; but it has been prepared especially for pupils who end their school education when, or even before, the ordinary high-school course is completed. It is confidently hoped also that those outside of schools who are desirous of learning something of Botany will find here an attractive introduction to this important science, for the further study of which the works of Gray, Bessey, and others are so admirably adapted.

In Part I. the subject of Structural Botany or Organography is presented in the customary form, yet a slight abridgment of the number of technical terms and the etymologies of the important ones given will, it is believed, be found improvements.

The numerous figures in Part II. will enable the pupils, even without the aid of microscopical appliances, to get a clear idea of the minute structure or histology of plants, upon which, to a large extent, physiology is based.

In Part III. the arrangement of the various groups of plants corresponds quite closely to that in recent publications by eminent botanists. Departures made by Bessey in his Botany seem desirable, and, therefore, have ‘been followed. Only a limited number of representative groups have been mentioned; and should the teacher find this number too great for mastery on the part of his pupils, a further abridgment can readily be made.

In Part IV. only a few, yet in general the most

PREFACE. i important, vegetable products have been mentioned and briefly described. The order of sequence of the groups is -that used by Weisner in his Rohstoffe des Pflanzenreiches, a book which is the source of much of the information, especially of that relating to anatomy, contained in this part.

The Appendix contains suggestions that will, it is hoped, be of advantage, especially to those who study without the assistance of a teacher.

All minute measurements have been given in fractions of an inch, although the great advantage of the use of the metric system is not in the least questioned. But pupils are not, as a rule, familiar with the latter, and can only slowly and gradually be taught to substitute it for what they have learned in early youth and practiced since. The same in substance may be said with reference to the Centigrade and Fahrenheit’s thermometers, the familiar scale of the latter being used in this work. Especial attention is called to the tables given in the Appendix of the equivalents of an inch in millimetres, also the equivalents of the degrees of Fahrenheit’s scale in degrees on the Centigrade scale.

Nearly three hundred of the illustrations are original. Figs. 228a and 824a were taken, by permission of the publishers, from Wood’s Class-book of Botany; Figs. 134, 135, and 308 from Gray’s Botany; Figs. 342, 343, 344, 345, 346, and 347 from Le Conte’s Geology; Figs. 148»

Vili PREFACE. 169, 182, 185, 188, 120, 221, 234, 237, 238, 241, 247, 248, 251, 253, 254, 257, 264, 266, 277a, 282, 300, and 301 from foreign authors, as Sachs, De Bary, and others. Twenty-two illustrations of ornamental plants were furnished by C. W. Seelye, editor of Vick’s Magazine, from publications of James Vick.

I would say finally that I have been assisted by my wife in the entire preparation of the book, and to her equally with myself is to be attributed any merit that it may contain.

Srate AGRICULTURAL CoLLEGE, Manuarran, Kansas, 1883, W. A. K

INTRODUCTION « 2 es ee et et ttt th te te we

Part I.—ORGANOGRAPHY

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THe CELL. ..... eee Fi mises Fit Socaaaereay ya Tup CELL-CONTENTS . 2. 4 ee ew eee ee ewe MINS Ose tes god 0 te, od. os san a ths Sok as a se) a) Fa ee Sid Gh See WATER «1. ee ee aoe Da Fas Sei Tar SEGRE aes ee aE RES FooD-ELEMENTS. 1... ess SBP iel ei Pe ed we a ee Ss ASSIMILATION AND METASTASIS . . 2 + 1 ee ee ee ee RESPIRATION. «2 1s ee eee Dea er er aera oer Pe r TEMPERATURE 1 0 ee eee te eee wee cee ees LIGHT. .... Re ese fa ee Ree te, Ste ita Yad Jane ua (Sb aia Jona MovEMENTS ..... SO ase ae SORE Bee we ES

Part III.—SYSTEMATIC BOTANY

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PAGE x CONTENTS.

CARPOSPOREE . 6 +e ee eee ee er eee ew ee os 136 BRYOPHYTA) +65) 2% coh fos ye? fetes ee ee exe els) os 4S PTERIDOPHYTA. 6 2 ee ee eee eww ee eee we ee 158 PHHNOGAMIA. «6 + 6 we ee te tt te oe ai ce a VST GYMNOSPERMH. 1 6 ee ee ee ew ee tt et ew wo ww LEZ ANGIOSPERMH «6 0 eee ee te ee ee sca es & 166 MonocoTyLEDONES......- Bee Shae wee a ee 169 DICOTYLEDONES. » 1 ee ee ee eee we ews a2 ete eer on ot LOA: GEOGRAPHICAL DISTRIBUTION. . 2 ss ee ee eee ee QL Possrts PLA Nis 55a as Sap Gey eee ese ww es ee tel ee 6 SDB

Part IV.—ECONOMIC BOTANY

THR RESINS) 2c: sesh ahh ee RL Sw ee SE Tur CaoutcHouc GROUP. .... aoyidend Wek a vel ee AC ae fo os QEE Opium AND CATECHU GROUP... 2.2 ee eee ees 265 VEGETABLE Fats AND WAK ...- 2. ee wee oo. » 268 CAMPHOR . «2 ee se ee wee Se ads ka Pen ey TRL ugh ta ae ee ES StarcH AND SuGAR ...... Suey Soe ale sy es MS) ee DS FIBRES. 2. 2 ee ee Ce ee wee ee ee ee te 2B Tur CoRTEX OR BARK... 1. 2. ee eee ee we ee 291 Woop. ...... a ge rae tah a a ae a ee 96 Roots AND RHIZOMES... 2. 6 2 6 2 eee we wwe >.» 308 TGBAVES: 20s: eee, ae ae 8 NES AS Ree cee Ae eee SG B0D FLOWERS. .... Mids A Ae rie ee Re rte B08 SEerps AND Fruits. .... ecdian ah Gaara PBs By ae ae Sos God, ee TOL: GALLS AND CRYPTOGAMS . 2. + 2 es ese eee eee e 320

Appendix

SUGGESTIONS FoR STUDYING. - 2. 2. 2 ee ee ee eo es 893 SUGGESTIONS FoR COLLECTING. ....... eee es. 823 Tur MICROSCOPE. . - 2 ee ee ee we we ee wee ew ww BAD Microscopic PREPARATIONS. . . « « Binet len sev ee Ye eh wl Se ee ODE Tor HERBARIUM... 22. eee ee wee erase «+ » 8282

GLOSSARY . + +e eee eS 31 TABLES OF EQUIVALENTS. «2 1 6s ee ee ee + + 889, 360

ELEMENTS OF BOTANY.

Introduction

Broroey is a term now used to denote the study of all living things or organisms, namely, Plants and Animals. These, as contrasted with minerals or inorganic matter, are, in general, distinguished by the possession of organs, or special parts of their structure, designed to perform certain functions. The very lowest or simplest forms of living matter, however, are often so homogeneous and structureless, or “ organless,” that they are with difficulty separated from some of the complex, inorganic substances; in other words, there is the most intimate connection between the mineral, or inorganic, and the organic kingdoms. Between the commoner and widely-divergent representatives of these, as, for example, between a crystal of quartz and a tree or a toad, there are numerous patent, distinguishing characteristics, besides the absence or presence of organs ; prominent among which is the fact of parentage, or power on the part of organisms to reproduce themselves, and so, by offspring, perpetuate their kind.

That department of Biology, which treats of plants, is called Borany. It is almost inseparable from Zoo.oey, which treats of Animals; for the lowest organisms can

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12 ELEMENTS OF BOTANY.

often be called plants with as much propriety as animals, and animals with as much propriety as plants, on account of the simplicity of their structure and the few characters they present, upon which a systematic classification may be based. It has been proposed to form another Group, called the Prorisra, to receive these low organisms; the higher representatives of the Vegetable and Animal Kingdoms are readily distinguished by many anatomical and physiological characters.

Plants feed on mineral or inorganic substances. Animals derive their food from plants. Many of them, as the herbivorous animals, feed exclusively on vegetation. Carnivorous animals, devouring the vegetable-feeders, depend no less really though indirectly on plants for food.

Plants in general consume carbonic dioxide, and liberate oxygen. This is not true, however, of the parasitic plants, called Fungi. Animals consume in respiration oxygen, and liberate carbonic dioxide. The two kingdoms are thus mutually dependent.

The surface expansion for absorption, etc., is very extensive in case of both plants and animals. In case of plants, however, it is mainly external, as the surface of the roots, rootlets, rhizoids, stems, and leaves; in case of animals it is, in the main, internal, as the alimentary canal, the vascular and respiratory vessels, etc.

Plants possess chlorophyll, that is, green coloring matter, by reason of which they are able to convert the inorganic food into organic matter. Fungi and other parasites and saprophytes are destitute of chlorophyll, and these plants appropriate to their own use the food assimilated by chlorophyll-bearing plants. Animals, with the exception of a very few low forms, do not possess chlorophyll.

INTRODUCTION. 13

Very many vegetable substances or products are ternary compounds, or composed mainly of oxygen, carbon, and hydrogen; while very many of the animal substances or products are quaternary compounds, or composed of oxygen, carbon, hydrogen, and nitrogen.

Most plants, but by no means all of them (especially the lower forms), are stationary, or have no power of locomotion; while animals, also with numerous exceptions, locomote freely from place to place.

Sensation is possessed by plants in a very much less marked degree than by animals.

The study of plants may be solely with reference -to their visible parts or organs, and this part of the science is called ORGANOGRAPRY, or Structural Botany. When the investigation touches the minute or microscopic structure of plants or their parts and products, it is called Minute Anatomy, or Hisrotoay. The study of the parts of the plant with reference to their functions or office, or their so-called vital actions, comes under the head of VEGE- TABLE PuysroLtocy. The classification of plants and what directly appertains to it constitutes Systematic Borany. All the plants of any region are called the Flora of that region. Fossrn Borany treats of fossil plants, or those which existed in previous geologic times, and whose remains or impressions are found in rock-strata. The application of botanical knowledge in the arts, industries or pursuits of life is designated by the term AprLieD Botany. This may be Agricultural, Horticultural, or Medical Botany, etc. Economic Borany is commonly used to indicate a study in general of the vegetable products and their uses.

Part I. Organography

1. If we examine any common plant, such as a Grass, Rose-bush, Willow, or an Oak, three distinct parts will be found, namely :

' I. Roor.

II. Srem.

ITI. Leaves,

2. The Root, or descending axis of the plant, generally grows downwards into the ground, sends out numerous branches, and thus firmly fixes the plant in its position. It also absorbs from the soil water or moisture, which contains plant food held in solution. Leaves, or scales representing leaves, are never found on the roots.

3. The Stem, or ascending axis, generally grows upwards, and furnishes the support for all the parts which grow above ground. It may be herbaceous,—that is, of soft tissue, like the Pansy,—or it may be woody, like the Lilae, or Willow-tree.

4. The Leaves are inserted on the stem or its branches. They are generally of a deep-green color and flattened shape. Their office is to convert the inorganic food, which has been absorbed by the roots and conveyed to them by the stem, into organic matier. From them more or less watery vapor is continually escaping.

5. Hairs, or Trichomes, may occur on any part of the plant, as on roots, stems, or leayes. They are mostly

ORGANOGRAPHY.

hair-like in shape, often very small, but they are sometimes long, and may form a dense covering, and hence afford protection for the plant. They may also take the shape of scales, glands, bristles, prickles, etc.

THE ROOT.

6. The Root is present in nearly all of the higher plants, as trees, shrubs, and. herbs, but wanting in Mosses, Liverworts, Fungi, and Alge. It is usually destitute of color, but may be brownish, yellowish, reddish, though never green, In case of some plants (Mosses, Liverworts, ete.), there are root-hairs, called rhizoids (Gr. rhiza, root), which have the same function, but not the same structure, as the true roots.

7. The root is generally found underground, -where it sends out numerous branches, without any particular order; and these, in turn, branch again and again into smaller roots, called Rootlets. The plant is thus firmly fixed in its place.

These rootlets, or their minute branches, are covered with numerous hairs, sometimes called fibrille (Fig. 1).

In Fig. 2 the terminal portion of a rootlet, with root-hairs much magnified, is shown. In

Fig. 1. Wheat in different stages (I, II, IIT, IV) of germination: 7, root with root-hairs; s, particles of adhering soil; st, stem,

THE ROOT. 17 many cases, as in the seedling of Wheat, Flax, etc., these may be seen by the unaided eye, appearing as a woolly covering. The special office of these is to absorb the dissolved food from the soil.

8. When aseed germinates, it generally sends a single root (radicle, Fig. 3,r.d.) downwards, which is called the primary root. This may continue to grow, and remain larger than any of its branches or side-roots which ZR it sends out, and in this case it is called the main, or tap-root.

g. The tap-root, when not woody (as in shrubs and trees), may become fleshy, that is, thickened, as, for example, in the Carrot, Turnip, etc. This is in consequence of a deposit of nourishment which has been elaborated or prepared in the ; green parts of the plant. When it >: is larger at the top, or where it joins ; the stem, and tapers gradually downwards, it is said to be conical (Fig. 4); if it is turnip-shaped, that is, very large above, tapering abruptly, and becoming very slender below, 3

Fig. 2. Portion of a root, with root-hairs, highly magnified. Fig. 3. The Bean in different stages of germination: cot, cotyledons; /, plumule; 7.d., radicle ; cau, caulicle ; us, leaves, it is napiform (Lat. napis, turnip; Fig. 5); when spindleshaped, or thick in the middle, and tapering to both ends, it is said to be fusiform (Lat. jusis, spindle; Fig. 6).

10. There may grow from the plantlet, when a seed sprouts, several roots, instead of a single one, as in the Indian Corn, Wheat, Pea, etc. (Fig. 1, etc.) In such case they are called multiple primary roots. Sometimes they become enlarged, as in the Sweet-potato, Dahlia, etc., and thus serve as reservoirs of plant food. They are then said to be tuberous (Fig. 7). In grasses and many other plants they are numerous and thread-like, and are called fibrous roots (Fig. 8).

11. Secondary roots may arise from the different parts of the plant,—stem and branches,—whether above or below ground. They are called adventitious roots.

They are common in creeping plants especially at the joints, and their production is favored by contact with moist soil. In the Trumpet Creeper, Poison Ivy, ete, they assist the plant in climbing, and, since they do not grow into the ground, they are called aerial roots.

12. Aerial roots are more common in moist tropical

Fig. 4. A conical root. Fig. 6. A napiform root. Fig. 6, A fusiform root, , Fig. 7. Tuberous roots. Fig. 8, Fibrous roots. -

THE ROOT. 19 countries, especially in deep forests where the light is partially excluded,—it being unfavorable to their development, A notable example is furnished by the Banyan-tree of India, and some other Fig-trees, whose outstretched branches send down adventitious roots, that grow into the soil, and thus become ‘supporting columns. The Screw-pine is sometimes wholly propped up by roots that originate some distance from the ground. The. Sugar- Cane produces aerial roots similar to those of Indian Corn, but they develop from joints higher up. The seeds of the Mangrove of the West Indies sprout before falling from the tree, and send a long root, or radicle, down into the mud, in which these trees grow, thus gaining a foothold before severing their connection with the parent tree.

13. Aerial roots, whose function is somewhat different from the above, are found in epiphytes (Gr. epi, upon; phyton, plant), or air-plants. They generally grow on other plants, as their name signifies, but their roots serve merely to give the plant attachment, and the food is derived wholly from the air. Many of the beautiful Orchids of the Tropics are of this nature. The Epidendron, or Tree Orchis (growing on a species of Magnolia), and the Tillandsia, or Spanish Moss (hanging in tufts or festoons from trees), of the Southern States, are epiphytes. Many Mosses, Lichens, ete., are epiphytic, though destitute of true roots.

14. Certain plants not only fix themselves to, but also draw their nourishment from, other plants. Such are parasites. They send their roots, or what answer functionally to them, into the tissue of their host and absorb the nourishment which the latter had prepared for its own use, True parasites are destitute of the green substance in leaves, called chlorophyll (Gr. chloros, green ; phyllon, leaf), in whose presence (in sunlight) the plant can convert the inorganic matter into plant food—that is, organic matter.

15. The Fungi (as Moulds, Blights, etc.) are parasitic either on living or decaying substances. The Beech-drops and Indian-pipe are attached to roots and draw their nourishment therefrom. The leafless Cuscuta, or Dodder, is a slender, yellowish parasite of peculiar nature. The seeds sprout in the ground, but the plantlet, as soon as it appears above the surface, seeks for plants around which to twine ; if unsuccessful it soon dies; but if it finds a proper plant, it sends its rootlets, in the form of suckers, into its host, by means of which it absorbs sufficient nourishment for its growth and development; the stem of the parasite then dies, and thus severs its connection with the soil.

16. The Mistletoe of. Europe, and the false Mistletoe of this country, have chlorophyll in their leaves, and are, therefore, capable of assimilation, that is, of converting inorganic into organic matter; or, in other words, of preparing their own food. Yet they do this only in part. They draw a portion of their food from the trees on which they grow, and are to that extent, therefore, parasitic.

The nature of the yellowish or whitish leafless plants, which are fixed to the ground, should not be misunderstood. They do not draw their nourishment from the soil, but from underground roots. Neither should all subterranean parts of plants be regarded as roots, since stems sometimes grow underground. Their true nature, however, is easily determined by the buds and scales (modified leaves) which they produce. Such, for example, are the Irish-potatoes, rootstock of Flag, etc,

THE STEM. a1

THE STEM.

17. The most striking differences in stems of various plants is in regard to their size and texture. A stem whose tissue is soft (mostly green) and not woody is said to be herbaceous. An herb which completes its growth and dies the same season is called an annual; a biennial herb, such as the Turnip, Carrot, etc., requires two years to complete its growth and produce seed ; an herb is perennial when the root continues to live for several years, although the stem every year dies down to the ground, a very small portion only remaining, from the buds of which the shoots arise the following year. If the stem is woody, though not growing to a great height, it is said to be fruticose (Lat. frutex, shrub), or shrubby; when approaching a tree in size it is arborescent (Lat. arbor, tree), and when forming a proper tree-trunk it is arboreous. me a . pe 18. The stem of every plant is vertical in its early stages of development; this direction is often maintained, when the stem is said to be erect. If it is prostrate or trailing it is said to be procumbent. A decumbent stem is one that reclines on the ground after having arisen at the base somewhat above it. A stem, climbing by tendrils or rootlets, is said to be scandent; when twining around other objects it is voluble. Stems which grow underground are called subterranean stems. 1g. The majority of stems and branches are more or less round (Fig. 9), but many of our common plants, for example, the whole family Labiate (“lip-shaped flowers”), have

Fig. 9. A round stem. Fig. 10. Asquare stem. Fig. 11. A flattened stem. Fig. 12. A winged stem.

square stems (Fig 10). Some plants, as the Wire-Grass (Poa compressa, L.), have flattened stems (Fig. 11); others may be winged (Fig. 12). Those of Grasses and Sedges are conspicuously jointed and sometimes hollow, and have received the special name of culm (Fig. 13). The trunk of the Palms, and the like, is called caudex.

20. Certain forms of branches are used “by gardeners for the purpose of propagating by buds. Such are Suckers, Stolons, Offsets, and Runners. Suckers arise from underground - stems. Stolons are trailing or reclining branches which take root where they touch the soil. Offsets are short Stolons, like those of the House-leek. Runners are slender, leafless creeping branches, which, when the full length is attained, take root at the tip, form a bud, and develop an independent plant. :

21. Some tendrils are slender branches destitute of leaves and intended for assistancein climbing. Examples are furnished by the Grape-Vine, Virginia Creeper, Squash, ete. (Fig. 14). They generally grow out straight until some slender object is reached, around which the tips

Fig. 18. Culm or stem of Grass. Fig. 14. Tendril (#) of the Wild Balsam-apple (Echinocystis), attached at the tip and coiled to the right (7) and to the left (2).

THE STEM. 98 hook. Then the whole tendril shortens by coiling up spirally, thus bringing the plant nearer the support. The

Virginia Creeper develops. the tendril-tips into adhering disks when it climbs walls or smooth trees (Fig. 15). Other tendrils, as of the Pea, etc., are modified leaves instead of branches. Spines, or thorns, are sometimes stunted and hardened branches, as in neglected Pear-trees, Plum-trees, ete. (Fig. 16).

22. Subterranean stems and branches ~ may seem on cursory examination to be little, if at all, different from roots. But they'are jointed, and roots are not; they have modified leaves in the form of scales—always absent in roots; buds may generally be found on them, but roots never produce buds. Four common types of subterranean stems are the Rhizome, Tuber, Corm, and Bulb. The rhizome (Gr. rhiza,

Fig. 15. Tendril, which ends in coils (¢) and disks (¢) of the Amfelopsis, or Virginia Creeper. Fig. 16. Spine or stunted branch of the Crab-apple. Fig. 17. Rhizome (7%) of Mint: 7, roots; s¢, stem. ‘ root) is very common, as in the Mint, Couch-grass, ete. ; it is merely a root-stock, or stem growing under the surface of the ground, producing roots, also leaf-scales and buds (Fig.17). Atuber is a thickened portion of a root-stock.

The Potato is the commonest example, the “eyes” being buds (Fig.18). The corm is a very short, thickened root-stock, with roots below and buds above.

23. The bulb is an extremely short root-stock, producing, like the corm, roots from the under side. It is covered with leaves, or the base of leaves, in the form of thickened scales. If the latter are broad, and cover all that is within, the bulb is said to be coated (Fig. 19), or tunicated (Lat. tunica, covering). But if the scales are narrow and separate, as in the Lily, the bulb is said to be sealy (Fig. 20). The small buds above ground, as in the axils of some Lilies, etc., are called bulblets. The bulb, like the corm and tuber, is a reservoir of

Fig. 18. Potato tuber (4); 7, roots; s#, stems. Fig. 19. A coated bulb. Fig. 20. A scaly bulb.

nourishment. The former contains the nourishment in the leaves (base of leaves), and the two latter have it in the thickened stem itself.

24. The Bud.—At definite places on the stem occur buds, which are simply undeveloped branches or shoots. The scales of the buds are small leaves, and that on which they are situated is the stem (as yet undeveloped). The bud at the end of the stem is called the terminal bud (Fig. 21, ter); the others are thé lateral buds. Of these, the majority occur in the axils of the leaves (or if the leaves have fallen, they may be seen just above the leaf-scar), and for this reason they are called axillary buds (Fig. 21, az). Sometimes one or two are lf produced on either side of or above j the axillary bud, and in such case they are called accessory buds (Fig. 21, ac). Occasionally their place of origin is indefinite or irregular; they are then called adventitious buds (Fig. 21, ad). Many of the. lateral buds fail to develop into branches the following year, often remaining dormant for several years; such are latent buds.

THE LEAF.

25. The Leaf is that organ of the plant which is intended primarily for the presentation of a large amount of surface expansion. Accordingly, we find it, as a rule, very broad and long compared with its thickness. Ordinary leaves, or foliage (Lat. folium, leaf), exhibit this

Fig. 21. Buds: zev, terminal ; ar, axillary.; ac, accessory; ad, adventitious, typical form ; besides these there are many modified forms, some of which have departed so far from the type that their true nature can be understood only when we see all the intermediate forms or gradations connecting the two extremes. Such are Cotyledons, Scales, Spines, Tendrils, Pitchers, y,, and Fly-traps.

26. The two halves into which a Pea, Bean, etc., readily divide are . ealled the cotyledons (Gr. kotula, cup), or seed-leaves (Fig 22, cot).

If they be observed, in case of the Pumpkin and certain other plants, some time after germination they will be found to have changed their : shape somewhat and become green, like ordinary leaves. As a rule, however, the cotyledons are simply to nourish the plantlet during germination. In the bulbscales is stored up food for the early growth of the plant the following season. This nourishment is consumed, in such bulbous plants as the Hyacinth, etc., by the production of flowers in advance of the leaves.

27. The leaves of underground stems are generally reduced to mere scales. These bud-scales, which protect the tender parts within, are modified leaves. A gradual transition between them and the

Fig. 22. Different stages in the germination of the Bean: cot, cotyledons: r, radicle ; #/, plumule. Fig. 23. Spines, which are modified leaves, of the Barberry,

THE LEAF. o7 first foliage leaves may often be traced, as in the Lilac, Hickory, etc. When spines occupy the place of leaves, they are modified forms of the q@, cae latter. In the Barberry all gra- & dations may be seen on a single shoot (Fig. 23). The leaf, or a portion of it, may become changed into a tendril for climbing, as in the Pea, Vetch, etc. (Fig. 24). 28. Very interesting #\ modifications of leaves \ are furnished by the Pitcher-plant (Sarracenia), Sundew (Dro- 2 sera), and the Venus’s Fly-trap (Dionea). ‘The leaves of Sarracenia are hollow cups or tubes (Fig. 25), covered within with hairs directed downwards. They are generally half-full of a liquid, into which insects may fall, and become macerated, and their juices are then absorbed by the plant. The Droseraisalsocar- ,, nivorous, feeding on small (\,Z insects which alight on and are held fast by viscid tentacles or hairs on the upper side of the leaf. The leaves of Dionea (Fig. 25a) have at the top two or three lobes furnished with a marginal