The Elements Of Botany, For Beginners And For Schools

THE ELEMENTS OF BOTANY

IVISON, BLAKEMAN, AND COMPANY NEW YORK AND CHICAGO Copyright , By Asa Gray . 1887....

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PREFACE.

This volume takes the place of the author's Lessons in Botany and Vegetable Physiology , published over a quarter of a century ago. It is constructed on the same lines, and is a kind of new and much revised edition of that successful work. While in some respects more extended, it is also more concise and terse than its predecessor. This should the better fit it for its purpose now that competent teachers are common. They may in many cases develop paragraphs into lectures, and fully illustrate po

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Section II. FLAX AS A PATTERN PLANT.

8. Growth from the Seed. Phanerogamous plants grow from seed, and their flowers are destined to the production of seeds. A seed has a rudimentary plant ready formed in it,—sometimes with the two most essential parts, i. e. stem and leaf, plainly discernible; sometimes with no obvious distinction of organs until germination begins. This incipient plant is called an Embryo . 9. In this section the Flax-plant is taken as a specimen, or type, and the development and history of common plants in gener

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Section III. MORPHOLOGY OF SEEDLINGS.

18. Having obtained a general idea of the growth and parts of a phanerogamous plant from the common Flax of the field, the seeds and seedlings of other familiar plants may be taken up, and their variations from the assumed pattern examined. 19. Germinating Maples are excellent to begin with, the parts being so much larger than in Flax that a common magnifying glass, although convenient, is hardly necessary. The only disadvantage is that fresh seeds are not readily to be had at all seasons. Fig.

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Section IV. GROWTH FROM BUDS: BRANCHING.

45. Most plants increase the amount of their vegetation by branching, that is, by producing lateral shoots. 46. Roots branch from any part and usually without definite order. Stems normally give rise to branches only at definite points, namely, at the nodes, and there only from the axils of leaves. 47. Buds (Fig. 72, 73 ). Every incipient shoot is a Bud ( 12 ). A stem continues its growth by its terminal bud ; it branches by the formation and development of lateral buds . As normal lateral buds

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Section V. ROOTS.

65. It is a property of stems to produce roots. Stems do not spring from roots in ordinary cases, as is generally thought, but roots from stems. When perennial herbs arise from the ground, as they do at spring-time, they rise from subterranean stems. 66. The Primary Root is a downward growth from the root-end of the caulicle, that is, of the initial stem of the embryo (Fig. 5-7 , 81 ). If it goes on to grow it makes a main or tap-root , as in Fig. 37 , etc. Some plants keep this main root throug

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Section VI. STEMS.

88. The Stem is the axis of the plant, the part which bears all the other organs. Branches are secondary stems, that is, stems growing out of stems. The stem at the very beginning produces roots, in most plants a single root from the base of the embryo-stem, or caulicle. As this root becomes a descending axis , so the stem, which grows in the opposite direction is called the ascending axis . Rising out of the soil, the stem bears leaves; and leaf-bearing is the particular characteristic of the s

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§ 1. LEAVES AS FOLIAGE.

121. This is tautological; for foliage is simply leaves: but it is very convenient to speak of typical leaves, or those which serve the plant for assimilation, as foliage-leaves, or ordinary leaves. These may first be considered. 122. The Parts of a Leaf. The ordinary leaf, complete in its parts, consists of blade , foot-stalk , or petiole , and a pair of stipules . 123. First the Blade or Lamina , which is the essential part of ordinary leaves, that is, of such as serve the purpose of foliage.

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§ 2. LEAVES OF SPECIAL CONFORMATION AND USE.

Fig. 169. A young Agave Americana, or Century-plant; fleshy-leaved. 165. Leaves for Storage. A leaf may at the same time serve both ordinary and special uses. Thus in those leaves of Lilies, such as the common White Lily, which spring from the bulb, the upper and green part serves for foliage and elaborates nourishment, while the thickened portion or bud-scale beneath serves for the storage of this nourishment. The thread-shaped leaf of the Onion fulfils the same office, and the nourishing matte

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§ 3. STIPULES.

174. A leaf complete in its parts consists of blade, leaf-stalk or petiole, and a pair of stipules. But most leaves have either fugacious or minute stipules or none at all; many have no petiole (the blade being sessile or stalkless); some have no clear distinction of blade and petiole; and many of these, such as those of the Onion and all phyllodia ( 166 ), consist of petiole only. 175. The base of the petiole is apt to be broadened and flattened, sometimes into thin margins, sometimes into a sh

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§ 4. THE ARRANGEMENT OF LEAVES.

181. Phyllotaxy , meaning leaf-arrangement, is the study of the position of leaves, or parts answering to leaves, upon the stem. Fig. 181. Alternate leaves, in Linden, Lime-tree, or Basswood. Fig. 182. Opposite leaves, in Red Maple. 182. The technical name for the attachment of leaves to the stem is the insertion . Leaves (as already noticed, 54 ) are inserted in three modes. They are Alternate (Fig. 181 ), that is, one after another, or in other words, with only a single leaf to each node; Oppo

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§ 1. POSITION AND ARRANGEMENT OF FLOWERS, OR INFLORESCENCE.

197. Flower-buds appear just where leaf-buds appear; that is, they are either terminal or axillary ( 47-49 ). Morphologically, flowers answer to shoots or branches, and their parts to leaves. 198. In the same species the flowers are usually from axillary buds only, or from terminal buds only; but in some they are both axillary and terminal. 199. Inflorescence , which is the name used by Linnæus to signify mode of flower-arrangement, is accordingly of three classes: namely, Indeterminate , when t

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§ 2. PARTS OR ORGANS OF THE FLOWER.

228. These were simply indicated in Section II. 16 . Some parts are necessary to seed-bearing; these are Essential Organs , namely, the Stamens and Pistils . Others serve for protection or for attraction, often for both. Such are the leaves of the Flower, or the Floral Envelopes . 229. The Floral Envelopes , taken together, are sometimes called the Perianth , also Perigone , in Latin form Perigonium . In a flower which possesses its full number of organs, the floral envelopes are of two kinds, n

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§ 3. PLAN OF FLOWER.

239. All flowers are formed upon one general plan, but with almost infinite variations, and many disguises. This common plan is best understood by taking for a type, or standard for comparison, some perfect , complete , regular , and symmetrical blossom, and one as simple as such a blossom could well be. Flowers are said to be Perfect ( hermaphrodite ), when provided with both kinds of essential organs, i. e. with both stamens and pistils. Complete , when, besides, they have the two sets of flor

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§ 4. MODIFICATIONS OF THE TYPE.

248. The Deviations , as they may be called, from the assumed type or pattern of flower are most various and extensive. The differences between one species and another of the same genus are comparatively insignificant; those between different genera are more striking; those between different families and classes of plants more and more profound. They represent different adaptations to conditions or modes of life, some of which have obvious or probable utilities, although others are beyond partic

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§ 5. ARRANGEMENT OF PARTS IN THE BUD.

276. Æstivation was the fanciful name given by Linnæus to denote the disposition of the parts, especially the leaves of the flower, before Anthesis , i. e. before the blossom opens. Præfloration , a better term, is sometimes used. This is of importance in distinguishing different families or genera of plants, being generally uniform in each. The æstivation is best seen by making a slice across the flower-bud; and it may be expressed in diagrams, as in the accompanying figures. 277. The pieces of

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Section IX. STAMENS IN PARTICULAR.

281. Andrœcium is a technical name for the staminate system of a flower (that is, for the stamens taken together), which it is sometimes convenient to use. The preceding section has dealt with modifications of the flower pertaining mainly to calyx and corolla. Those relating to the stamens are now to be indicated. First as to 282. Insertion, or place of attachment. The stamens usually go with the petals. Not rarely they are at base Epipetalous , that is, inserted on (or adnate to) the corolla, a

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§ 1. ANGIOSPERMOUS OR ORDINARY GYNŒCIUM.

300. Gynœcium is the technical name for the pistil or pistils of a flower taken collectively, or for whatever stands in place of these. The various modifications of the gynœcium and the terms which relate to them require particular attention. 301. The Pistil , when only one, occupies the centre of the flower; when there are two pistils, they stand facing each other in the centre of the flower; when several, they commonly form a ring or circle; and when very numerous, they are generally crowded i

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§ 2. GYMNOSPERMOUS GYNŒCIUM.

313. The ordinary pistil has a closed ovary, and accordingly the pollen can act upon the contained ovules only indirectly, through the stigma. This is expressed in a term of Greek derivation, viz.:— Angiospermous , meaning that the seeds are borne in a sac or closed vessel. The counterpart term is Gymnospermous , meaning naked-seeded. This kind of pistil, or gynœcium, the simplest of all, yet the most peculiar, characterizes the Pine family and its relatives. Fig. 337. A pistil, that is, a scale

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Section XI. OVULES.

317. Ovule (from the Latin, meaning a little egg) is the technical name of that which in the flower answers to and becomes the seed. Fig. 340. A cluster of ovules, pendulous on their funicles. 318. Ovules are naked in gymnospermous plants (as just described), in all others they are enclosed in the ovary. They may be produced along the whole length of the cell or cells of the ovary, and then they are apt to be numerous, or only from some part of it, generally the top or the bottom. In this case t

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Section XII. MODIFICATIONS OF THE RECEPTACLE.

Fig. 356. Longitudinal section of flower of Silene Pennsylvanica, showing stipe between calyx and corolla. Fig. 357. Flower of a Cleome of the section Gynandropsis, showing broadened receptacle to bear petals, lengthened stipe below the stamens, and another between these and pistil. Fig. 358. Pistil of Geranium or Cranesbill. Fig. 359. The same, ripe, with the five carpels splitting away from the long beak (carpophore), and hanging from its top by their recurving styles. 323. The Torus or Recept

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§ 1. ADAPTATIONS FOR POLLINATION OF THE STIGMA.

329. These various and ever-interesting adaptations and processes are illustrated in the "Botanical Text Book, Structural Botany," chap. VI. sect. iv., also in a brief and simple way in "Botany for Young People, How Plants Behave." So mere outlines only are given here. 330. Sometimes the application of pollen to the stigma is left to chance, as in diœcious wind-fertilized flowers; sometimes it is rendered very sure, as in flowers that are fertilized in the bud; sometimes the pollen is prevented

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§ 2. ACTION OF POLLEN, AND FORMATION OF THE EMBRYO.

343. Pollen-growth. A grain of pollen may be justly likened to one of the simple bodies ( spores ) which answer for seeds in Cryptogamous plants. Like one of these, it is capable of germination. When deposited upon the moist surface of the stigma (or in some cases even when at a certain distance) it grows from some point, its living inner coat breaking through the inert outer coat, and protruding in the form of a delicate tube. This as it lengthens penetrates the loose tissue of the stigma and o

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Section XIV. THE FRUIT.

345. Its Nature. The ovary matures into the Fruit. In the strictest sense the fruit is the seed-vessel, technically named the Pericarp . But practically it may include other parts organically connected with the pericarp. Especially the calyx, or a part of it, is often incorporated with the ovary, so as to be undistinguishably a portion of the pericarp, and it even forms along with the receptacle the whole bulk of such edible fruits as apples and pears. The receptacle is an obvious part in blackb

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Section XV. THE SEED.

380. Seeds are the final product of the flower, to which all its parts and offices are subservient. Like the ovule from which it originates, a seed consists of coats and kernel. Fig. 414. Seed of a Linden or Basswood cut through lengthwise, and magnified, the parts lettered: a , the hilum or scar; b , the outer coat; c , the inner; d , the albumen; e , the embryo. 381. The Seed-coats are commonly two ( 320 ), the outer and the inner. Fig. 414 shows the two, in a seed cut through lengthwise. The

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§ 1. ANATOMICAL STRUCTURE AND GROWTH.

394. Growth is the increase of a living thing in size and substance . It appears so natural that plants and animals should grow, that one rarely thinks of it as requiring explanation. It seems enough to say that a thing is so because it grew so. Growth from the seed, the germination and development of an embryo into a plantlet, and at length into a mature plant (as illustrated in Sections II. and III. ), can be followed by ordinary observation. But the embryo is already a miniature plantlet, som

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§ 3. ANATOMY OF ROOTS AND STEMS.

423. This is so nearly the same that an account of the internal structure of stems may serve for the root also. 424. At the beginning, either in the embryo or in an incipient shoot from a bud, the whole stem is of tender cellular tissue or parenchyma. But wood (consisting of wood-cells and ducts or vessels) begins to be formed in the earliest growth; and is from the first arranged in two ways, making two general kinds of wood. The difference is obvious even in herbs, but is more conspicuous in t

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§ 4. ANATOMY OF LEAVES.

439. The wood in leaves is the framework of ribs, veins, and veinlets ( 125 ), serving not only to strengthen them, but also to bring in the sap, and to distribute it throughout every part. The cellular portion is the green pulp, and is nearly the same as the green layer of the bark. So that the leaf may properly enough be regarded as a sort of expansion of the fibrous and green layers of the bark. It has no proper corky layer; but the whole is covered by a transparent skin or epidermis , resemb

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§ 5. PLANT FOOD AND ASSIMILATION.

445. Only plants are capable of originating organizable matter, or the materials which compose the structure of vegetables and animals. The essential and peculiar work of plants is to take up portions of earth and air (water belonging to both) upon which animals cannot live at all, and to convert them into something organizable; that is, into something that, under life, may be built up into vegetable and animal structures. All the food of animals is produced by plants. Animals live upon vegetabl

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§ 6. PLANT WORK AND MOVEMENT.

458. As the organic basis and truly living material of plants is identical with that of animals, so is the life at bottom essentially the same; but in animals something is added at every rise from the lowest to highest organisms. Action and work in living beings require movement. 459. Living things move; those not living are only moved. Plants move as truly as do animals. The latter, nourished as they are upon organized food, which has been prepared for them by plants, and is found only here and

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§ 1. KINDS AND RELATIONSHIP.

520. Plants and animals have two great peculiarities: 1st, they form themselves; and 2d, they multiply themselves. They reproduce their kind in a continued succession of 521. Individuals. Mineral things occur as masses , which are divisible into smaller and still smaller ones without alteration of properties. But organic things (vegetables and animals) exist as individual beings . Each owes its existence to a parent, and produces similar individuals in its turn. So each individual is a link of a

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§ 2. NAMES, TERMS, AND CHARACTERS.

535. The name of a plant is the name of its genus followed by that of the species. The name of the genus answers to the surname (or family name); that of the species to the baptismal name of a person. Thus Quercus is the name of the Oak genus; Quercus alba , that of the White Oak, Q. rubra , that of Red Oak, Q. nigra , that of the Black-Jack, etc. Botanical names being Latin or Latinized, the adjective name of the species comes after that of the genus. 536. Names of Genera are of one word, a sub

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§ 3. SYSTEM.

547. Two systems of classification used to be recognized in botany,—the artificial and the natural; but only the latter is now thought to deserve the name of a system. 548. Artificial classifications have for object merely the ascertaining of the name and place of a plant. They do not attempt to express relationships, but serve as a kind of dictionary. They distribute the genera and species according to some one peculiarity or set of peculiarities (just as a dictionary distributes words accordin

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§ 1. COLLECTION, OR HERBORIZATION.

556. As much as possible, plants should be examined in the living state, or when freshly gathered. But dried specimens should be prepared for more leisurely examination and for comparison. To the working botanist good dried specimens are indispensable. 557. Botanical Specimens , to be complete, should have root or rootstock, stem, leaves, flowers, both open and in bud, and fruit. Sometimes these may all be obtained at one gathering; more commonly two or three gatherings at different times are re

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§ 2. HERBARIUM.

567. The botanist's collection of dried specimens, ticketed with their names, place, and time of collection, and systematically arranged under their genera, orders, etc., forms a Hortus Siccus or Herbarium . It comprises not only the specimens which the proprietor has himself collected, but those which he acquires through friendly exchanges, or in other ways. The specimens of an herbarium may be kept in folded sheets of paper; or they may be fastened on half-sheets of thick and white paper, eith

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§ 3. INVESTIGATION AND DETERMINATION OF PLANTS.

570. The Implements required are a hand magnifying glass, a pocket lens of an inch or two focus, or a glass of two lenses, one of the lower and the other of the higher power; and a sharp penknife for dissection. With these and reasonable perseverance the structure of the flowers and fructification of most phanerogamous plants and Ferns can be made out. But for ease and comfort, as well as for certainty and right training, the student should have some kind of simple stage microscope, and under th

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§ 4. SIGNS AND ABBREVIATIONS.

576. For a full account of these, whether of former or actual use, see "Structural Botany" of the "Botanical Text Book," pp. 367, 392, as also for the principles which govern the accentuation of names. It is needful here to explain only those used in the Manuals and Floras of this country, for which the present volume is an introduction and companion. They are not numerous. 577. In arranging the species, at least those of a large genus, the divisions are denoted and graduated as follows: The sig

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ABBREVIATIONS OF THE NAMES OF BOTANISTS.

For the convenience of unclassical students, the commoner Latin and Greek words (or their equivalents in English form) which enter into the composition of botanical names, as well as of technical terms, are added to this Glossary. The numbers refer to pages. A , at the beginning of words of Greek derivation, commonly signifies a negative, or the absence of something; as a petalous, without petals; a phyllous, leafless, &amp;c. In words beginning with a vowel, the prefix is an ; as an anthero

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