Complete Text (Part 3)

study of the plant with the full-grown herb or tree, adorned with flowers or laden with fruit? Or shall we commence with the seedling just rising from the ground? On the whole, we may get a clearer idea of the whole life and structure of plants if we begin at the beginning, that is, with the plantlet springing from the seed, and follow it throughout its course of growth. This also agrees best with the season in which the study of Botany is generally commenced, namely, in the spring of the year, when the growth of plants from the seed can hardly fail to attract attention. Indeed, it is this springing forth of vegeta- tion from seeds and buds, after the rigors of our long winter, — clothing the earth’s surface almost at once with a mantle of freshest verdure,— which gives to spring its greatest charm. Even the dullest beholder, the least observant of Nature at other seasons, can then hardly fail to ask: What are plants? How do they live and grow? What do they live upon? What is the object and use of vegetation in general, and of its particular and wonderfully various forms? ‘These questions it is the object of the present Lessons to answer, as far as possible, in a simple way. 13. A reflecting as well as observing person, noticing the re- semblances between one plant and another, might go on to inquire whether plants, with all their manifold diversities of form and appearance, are not all constructed on one and the same general plan. It will become apparent, as we proceed, that this is the case ;— that one common plan may be discerned, which each par- ticular plant, whether herb, shrub, or tree, has followed much more closely than would at first view be supposed. The differences, wide as they are, are merely incidental. What is true in a general way of any ordinary vegetable, will be found to be true of all, only with great variation in the details. In the same language, though in varied phrase, the hundred thousand kinds of plants repeat the same LESSON 2.) GROWTH OF THE PLANT FROM THE SEED. 5 story,—are the living witnesses and illustrations of one and the same plan of Creative Wisdom in the vegetable world. So that the study of any one plant, traced from the seed it springs from round to the seeds it produces, would illustrate the whole subject of vege- table life and growth. It masters little, therefore, what particular plant we begin with. 14. The Germinating Plantlet, Take for example a seedling Maple, Sugar Maples may be found in abundance in many places, starting Yrom the seed (i. e. germinating) in early spring, and Red Maples at the beginning of summer, shortly after the fruits of the season have ripened and fallen to the ground. A pair of narrow green leaves raised on a tiny stem make up the whole plant at its first appearance (Tig. 4). Soon a root appears at the lower end of this stemlet ; then a little bud at its upper end, between the pair of leaves, which soon grows into a second joint or stem bearing another pair of leaves, resembling the ordinary leaves of the Red Maple, which the first did not. Figures 5 and 6 represent these steps in the growth. 15. Was this plantlet formed in the seed at the time of germination, something as the chick = is formed in the egg during the process of incu- bation ?* Or did it exist before in the seed, ready formed? To decide this question, we have only to inspect a sound seed, which in this instance requires no microscope, nor any other a instrument than a sharp knife, by which the coats of the seed (previously soaked in water, if dry) may be laid open. We find within the seed, in this case, the little plantlet ready formed, and nothing else (Fig. 2);— namely, a pair of leaves like those of the earliest seedling (Fig. 4), only smaller, borne on a stemlet just like that of the seedling, only much shorter, and all snugly coiled up within the protecting seed-coat. The plant then exists beforehand in the seed, in miniature. It was not formed, but oni devel- FIG. 1. A winged frutt of Red Maple, with the seed-bearing portion cut open, to show the seed. 2. This seod cut open to show the embryo plantiet within, enlarged. 3. The embryo mn out whole, and partly unfolded. 4. The samo after it has begun to grow ; of the natural size. 1* 6 GROWTH OF THE PLANT FROM THE SEED. [LESSON 2, oped, in germination ; when it had merely to unfold and grow, — to elongate its rudimentary stem, which takes at the same time an upright position, so as to bring the leaf-bearing end into the light and air, where the two leaves expand; while from the opposite end, now pushed farther downwards into the soil, the root begins to grow. All this is true in the main of all plants that spring from real seeds, although with great diversity in the particulars. At least, there is hardly an excep- tion to the fact, that the plantlet exists ready formed in the seed, in some shape or other. 16. The rudimentary plantlet contained in the seed is called an Hméryo. Its little stem is named the Jadicle, because it was supposed to be the root, when the difference between the root and stem was not so well known as now. It were better to name it the Cauliele (i. e. little stem); but it is not expedient to change old names. The seed-leaves it bears on its sum- mit (here two in number) are technically called Cotylédons. The little bud of undeveloped leaves which is to be found between’ the co- 5 tyledons before germination in many cases (as in the Pea, Bean, Fig. 17, &c.), has been named the Plumule. 17. In the Maple (Fig. 4), as also in the Morning-Glory (Fig. 28), and the like, this bud, or plumule, is not seen for some days after the seed-leaves are expanded. But soon it appears, in the Maple as a pair of minute leaves (Fig. 5), erelong raised on a stalk ance above the cotyledons. The which carries them up to some dis plantlet (Fig. 6) now consists, above ground, of two pairs of leaves, 1. the cotyledons or seed-leaves, borne on the summit of the nal stemlet (the radicle); and 2. a pair of ordinary leaves, raised on a second joint of stem which has grown from the top of the first. Later, a third pair of leaves is formed, and raised on a third joint of stem, proceeding from the summit of the second (Fig. 7), just as that did from the first; and so on, until the germi- nating plantlet becomes a tree. FIG. 5. Ge 1g Red Maple, which has produced its root beneath, and is developing 2 second pair of leaves above. 6, Same, further advanced. LESSON 2.] GROWTH OF THE PLANT FROM THE SEED. 7 18. So the youngest seedling, and even the embryo in the seed, is already an epitome of the herb or tree. It has a stem, from the lower end of which it strikes root ; and it has leaves. The tree itself in its whole vegetation has nothing more in kind. ‘To become a tree, the plantlet has only to repeat itself upwardly by producing more similar parts, —that is, new por- tions of stem, with new and larger leaves, in succession, — while beneath, it pushes its root deeper and deeper into the soil. 19. The Opposite Growth of Root and Stem began at the beginning of germi- nation, and it continues through the whole life of the plant. While yet buried in the soil, and perhaps in total darkness, as soon as it begins to grow, the stem end of the embryo points towards the light, — curving or turning quite round if it happens to lie in some other direction, — and stretches upwards into the free air and sunshine ; while the root end as uniformly avoids the light, bends in the opposite direction to do so if necessary, and ever seeks to bury itself more and more in the earth’s bosom. How the plantlet makes these moyements we cannot explain. But the object of this instinct is obvious. It places the plant from the first in the proper position, with its roots in the moist soil, from which they are to absorb nourishment, and its leaves in the light and air, where alone they can fulfil their office of digesting what the roots absorb. 20. So the seedling plantlet finds itself provided with all the organs of vegetaiion that even the oldest plant possesses, — namely, root, stem, and leaves; and has these placed in the situation where each is to act, — the root in the soil, the foliage in the light and air. Thus established, the plantlet has only to set about its proper work. 21. The different Mode of Growtk of Root and Stem may also be here mentioned, Each grows, not only in a different direction, but in a different way. The stem grows by producing a set of joints, each from FIG. 7. Germinating Red Maple, further developed. 8 GROWTH OF THE PLANT FROM THE SEED. [LESSON 2, the summit of its predecessor; and each joint elongates throughout every part, until it reaches its full length. The root is not composed of joints, and it lengthens only at the end. The stem in the embryo (viz. the radicle) has a certain length to begin with. In the pump- kin-seed, for instance (Fig. 9), it is less than an eighth of an inch long: but it grows in a few days to the length of one or two inches (Fig. 10), or still more, if the seed were deeper covered by the soil. It is by this elongation that the seed-leaves are raised out of the soil, so as to expand in the light and air. The length they acquire varies with the depth of the covering. When large and strong seeds are too deeply buried, the stemlet sometimes grows to the length of several inches in the endeavor to bring the seed-leaves to the sur- face. The lengthening of the succeeding joints of the stem serves to separate the leaves, or pairs of leaves, from one another, and to ex- pose them more fully to the light. 22. The rot, on the other hand, begins by a new formation at the base of the embryo stem; and it continues to increase in length solely by additions to the extremity, the parts once formed scarcely elongating at all afterwards. This mode of growth is well adapted to the circumstances in which roots are placed, leaving every part undisturbed in the soil where it was formed, while the ever-advan- cing points readily insinuate themselves into the crevices or looser portions of the soil, or pass around the surface of solid obstacles. LESSON 3.] GROWTH OF THE PLANT FROM THE SEED. 9 LESSON IIL GROWTH OF THE PLANT FROM THE SEED. — Continued. 23. Soa plant consists of two parts, growing in a different manner. ‘as well as in opposite directions. One part, the root, grows down- wards into the soil: it may, therefore, be called the descending axis. The other grows upwards into the light and air: it may be called the ascending axis. The root grows on continuously from the ex- tremity, and so does not consist of joints, nor docs it bear leaves, or anything of the kind. he stem grows by a succession of joints, each bearing one or more leaves on its summit. Root on the one hand, and stem with its foliage on the other, make up the whole plantlet as it springs from the seed; and the full-grown herb, shrub, or tree has nothing more in kind, —only more in size and number. Before we trace the plantlet into the herb or tree, some other cases of the growth of the plantlet from the seed should be studied, that we may observe how the same plan is worked out under a variety of forms, with certain differences in the details. ‘he mate- rials for this study are always at hand. We have only to notice what takes place all around us in spring, or to plant some consmon seeds in pots, keep them warm and moist, and watch their germination. 24. The Germinating Plantlet feeds on Nourishment provided beforehand. The embryo so snugly ensconced in the seed of the Maple (Fig. 2, 3,4) has from the first a miniature stem, and a pair of Ieaves already green, or which become green as soon as brought to the light. It has only to form a root by which to fix itself to the ground, when it becomes a perfect though diminutive vegetable, capable of providing for itself. This root can be formed only out of proper material ; neither water nor anything else which the plantlet is imbibing from the earth will answer the purpose. The proper material is nourish- ing matter, or prepared food, more or less of which is always pro- vided by the parent plant, and stored up in the seed, either ix the embryo itself, or around it. Inthe Maple, this nourishment is stored up in the thickish cotyledons, or seed-leaves. And there is barely enough of it to make the beginning of a root, and to provide for the lengthening of the stemlet so as to, bring up the unfolding seed-leaves where they may expand to the light of day. But when this is done, S&F_2 10 GROWTH OF THE PLANT FROM THE SEED. [LESSON 3. the tiny plant is already able to shift for itself; — that is, to live and continue its growth on what it now takes from the soil and from the air, and elaborates into nourishment in its two green leaves, under the influence of the light of the sun. 25. In most ordinary plants, a larger portion of nourishment is provided beforehand in the seed; and the plantlet consequently is not so early or so entirely left to its own resources. Let us examine a number of cases, selected from very common plants. Sometimes, as has just been stated, we find this 26. Deposit of Food in the Embryo itself. And we may observe it in every gradation as to quantity, from the Maple of our first illus- tration, where there is very little, up to the Pea and the Horsechestnut, where there is as much as there possibly can be. If we strip off the coats from the large and flat seed of a Squash or Pumpkin, we find nothing but the em- bryo within (Fig. 9); and almost the whole bulk of this consists of the two seed-leaves. That these contain a good supply of nourishing matter, is evident from their sweet taste and from their thickness, although there is not enough to obscure their leaf-like appearance. It is by feeding on this supply of nour- ishment that the germinating Squash or Pumpkin (Fig. 10) grows so rapidly and so vigorously from the seed, — lengthening its stemlet to more than twenty times the length it had in the seed, and thickening it in proportion, — sending out at once a number of roots from its lower end, and soon developing the plumule (16) from its upper end into a third leaf: meanwhile the two cotyledons, relieved from the nourishment with which their tissue was gorged, have expanded into useful green leaves. 27. For a stronger instance, take next the seed of a Plum or Peach, or an Almond, or an Apple-seed (Fig. 11, 12), which shows Fic, 20. The s: Embryo of a Pumpkin, of the natural size; the cotyledons a little opened 1e, whien it has germinated. LESSON 3.] GROWTH OF THE PLANT FROM THE 8EED. i the same thing on a smaller scale. The embryo, which here also makes up the whole bulk of the kernel of the seed, differs from that of the Pumpkin only in having the seed-leaves more thickened, by the much larger quantity of nourishment stored up in their tissue,—so large and so pure in- deed, that the almond becomes an article of food. Fed by this abundant supply, the second, and even the third joints of the stem, with their leaves, shoot forth as soon as the stemlet comes to the surface of the soil. The Beech-nut (Fig. 13), with its sweet and eatable kernel, consisting mainly of a pair of seed-leaves folded together, and gorged with nourishing matter, offers another instance of the same sort: this ample store to feed upon enables the germinating plantlet to grow with remarkable vigor, and to develop a second joint of stem, with its pair of leaves (Fig. 14), before the first pair has expanded or the root has ob- tained much foothold in the soil. 28. A Bean affords a similar and more familiar illustration. Here the co- tyledons in the seed (Fig. 16) are so thick, that, although they are raised out of ground in the ordinary way in ger- mination (Fig. 17), and turn greenish, yet they never succeed in becoming leaf- like, — never display their real nature of leaves, as they do so plainly in the Ma- ple (Fig. 5), the Pumpkin (Fig. 10), the Morning-Glory (Fig. 8, 26-28), &c. Turned to great account as magazines of food for the germinating plantlet, they fulfil this special office admirably, but An Apple-seed cut through lengtawise, showing the embryo with it 1. The enibryo of the Apple, taken out whole, its cotyledons partly separated A Beech-nut, cut across, 14. Beginning geemination of the Beech, showing the plumule growin the cotyledons have