Aedile

“ Each leaf is traversed by two fibro-vascular bundles of entirely different structure from those of the ferns. Each is divided into two nearly equal parts, the wood (x) lying toward the inner, flat side of the leaf, the bast (T) toward the outer, convex side. This type of bundle, called “collateral,” is the common form found in the stems and leaves of seed plants. The cells of the wood or xylem are rather larger than those of the bast or phloem, and have thicker walls than any of the phloem cells, except the outermost ones which are thick-walled fibres like those under the epidermis. ”

“ In the experiment already recorded on the germination of seeds the interest is by no means confined to that which attaches itself to the arrest of the organizing functions of the seed, those namely which manifest themselves in the development of the radicle, and plumule, and other organs of the young plant. ”

“ Stems or branches which remain under ground give out roots as freely as roots themselves give off branches. Stems which creep on the ground most commonly root at the joints; so will most branches when bent to the ground, as in propagation by layering; and propagation by cuttings equally depends upon the tendency of the cut end of a shoot to produce roots. Thus, a piece of a plant which has stem and leaves, either developed or in the bud, may be made to produce roots, and so become an independent plant. ”

“ The ovule, as the female cell with its immediate surrounding tissue is termed, becomes inclosed with one or more coats of varying thickness, and, when the whole structure has reached maturity and is ready to separate from the parent-plant, we have the familiar body known as a seed. The seed is an independent plant-structure designed to develop into a mature herb, shrub, or tree, when the conditions are favorable for its germination and growth. ”

“ We must now consider closely the phenomena connected with the growth of an individual plant, which will illustrate the operation of physical influences throughout the vegetable world. The process by which the embryo, secured in the seed, is developed, is our first inquiry.
A seed is a highly carbonized body, consisting of integuments and embryo: between these, in most seeds, lies a substance called the albumen, or perisperm. The embryo contains the elements of the future plant—the cotyledons, the plumule, and the radicle ”

“ In these, the nucleus of the seed is not properly a monocotyledonous embryo, but has an appearance and economy more nearly resembling those of the tuber of a root; for, instead of being distinguishable into a cotyledon, a plumula and radicula, and of germinating in a determinate manner and from a single point, it is composed of a mass whose internal structure is uniform, and on the surface of which frequently more than one germinating point is observable. ”

“ Forms of Stems.—Stems may grow in many ways. Let the pupils compare the habits of growth of the seedlings they have studied. The Sunflower and Corn are erect. This is the most usual habit, as with our common trees. The Morning Glory is twining, the stem itself twists about a support. The Bean, Pea and Nasturtium are climbing. The stems are weak, and are held up, in the first two by tendrils, in the last by the twining leaf-stalks. ”

“ The seed is the plant contracted upon its centre, it is the heavy mineral mass, which can only undergo changes by the operation of the other elements, like as it arrived only at completion by the operation of the floral pollen. This acts upon it when within the dry ovary, like the water and oxygen in the dry earth. ”

“ I have just said that the ribs—and might have said, farther, the stalk that sustains them—are knit out of the tissue of the leaf. But what is the leaf tissue itself knit out of? One would think that was nearly the first thing to be discovered, or at least to be thought of, concerning plants,—namely, how and of what they are made. We say they 'grow.' But you know that they can't grow out of nothing;—this solid wood and rich tracery must be made out of some previously existing substance. What is the substance?—and how is it woven into leaves.—twisted into wood? ”

“ The matured seed, with embryo ready to germinate and reproduce the kind, completes the cycle of the vegetable life in a phanerogamous plant, the account of which began with the seed and seedling.
Section XVI. VEGETABLE LIFE AND WORK.
393. The following simple outlines of the anatomy and physiology of plants (3) are added to the preceding structural part for the better preparation of students in descriptive and systematic botany; also to give to all learners some general idea of the life, growth, intimate structure, and action of the beings which compose so large a part of organic nature. ”

“ PROFESSOR OF CHEMISTRY IN THE UNIVERSITY OF MICHIGAN.
TO form the seed seems to be the chief end of the plant. When in the vigor of its own maturity, and when receiving the sun's strongest rays and the earth's richest nourishment, the plant gathers all its resources, and devotes them to the building of the seed. When done, the seed itself, the embryo, commonly possesses little substance and serves little use beyond its primary purpose, the reproduction of the plant. ”

“ The roots of air-plants, such as certain orchids, draw their nourishment from the air.
The experiment of marking roots and stem has been already tried, but it should be repeated. Repetition of experiments is always desirable, as it fixes his conclusions in the pupil's mind. The stem grows by a succession of similar parts, phytomera, each part, or phyton, consisting of node, internode, and leaf. Thus it follows that stems must bear leaves. The marked stems of seedlings show greater growth towards the top of the growing phyton. It is only young stems that elongate throughout. ”

“ As the kernel swells with heat and moisture, its starches and albumens get oxidised and produce the motions and rearrangements of particles that result in the growth of a new plant. First a little head rises towards the sunlight and a little root pushes downward towards the moist soil beneath. The business of the root is to collect water for the circulating medium—the sap or blood of the plant—as well as a few mineral matters required for its stem and cells ”

“ THE CELL.
If we make a thin slice across the stem of a rapidly growing plant,—e.g. geranium, begonia, celery,—mount it in water, and examine it microscopically, it will be found to be made up of numerous cavities or chambers separated by delicate partitions. Often these cavities are of sufficient size to be visible to the naked eye, and examined with a hand lens the section appears like a piece of fine lace, each mesh being one of the chambers visible when more strongly magnified. These chambers are known as “cells,” and of them the whole plant is built up. ”

“ When nature has provided a soil, her next care is to perfect the growth of her seeds and then to disperse them. This is effected by the structure and arrangement of the seed varying according to the nature of its particular habitat. When the seed, or mature ovule, is ripe, it bursts the capsule in which it is contained and falls to the ground, or is scattered by the wind. ”

“ All the planetary elements belong to germination, and to growth the Cosmical also with all its actions. To germination belongs earth, water, and air; to growth, light, heat, and gravity; with all the four mineral classes also, such as earth, salt, Inflammable, and metal. The plant contains silicious and calcareous earth, salts, coal with sulphur, and lastly, iron.
1478. Germination is the disjunctive emergence wrought by means of moisture, heat and oxydation in the processes of decomposition and fermentation. No seed germinates in irrespirable kinds of air. ”

“ A tree differs from a seed in every respect—in bulk, in structure, in colour, in form, in chemical composition. Yet is the one changed in the course of a few years into the other: changed so gradually, that at no moment can it be said—Now the seed ceases to be and the tree exists. What can be more widely contrasted than a newly-born child and the small, semi-transparent, gelatinous spherule constituting the human ovum? The infant is so complex in structure that a cyclopædia is needed to describe its constituent parts. ”

“ But if, in lieu of either plan, we follow the original design of Nature by covering the seed with moist earth, the chemical changes which take place within it, still resulting in heat and motion, produce that special form of movement which we know as germination. New cells form themselves about the feathery head, a little sprout pushes timidly its way through the surrounding soil, and soon a pair of rounded leaves or a spike of pointed blades may be seen spreading a mass of delicate green toward the open sunlight overhead. ”

“ For the hidden primordial elements of metals and stones lie concealed in the earth, as those of herbs and plants do in its outer crust. For the soil dug out of a deep well, where would seem to be no suspicion of a conception of seed, when placed on a very high tower, produces, by the incubation of sun and sky, green herbage and unbidden weeds; and those of the kind which grow spontaneously in that region, for each region produces its own herbs and plants, also its own metals. ”

“ Do you know how nature plants them? A seed starts and becomes a small plant on the surface of the leaf mould or a little beneath; little roots push downward and to right and left; and later, after getting a good hold below with numerous branchlets, the slender roots shorten and tug away at the tiny bulb above, as much as to say, "Come down a little into mother earth, for cold winter is approaching and there will be danger from frost." The young bulb is drawn down an inch more or less, the slender roots perish with the growing year, but the bulb is preserved. ”

“ 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 outer coat is often hard or crustaceous, whence it is called the Testa, or shell of the seed; the inner is almost always thin and delicate. ”

“ But the most substantial reasons given for the composure of the Seed are grounded upon Circulation, that the seminal Particles are separated and filtrated from the Blood by the Testicles; and Anatomists acquainted with the Structure of the Testicles, say, that the Seed is produc’d by a continual Filtration of several Particles, which being gather’d into a 96Body, make a Liquor that is qualify’d for the forming of a Man. ”

“ All those familiar with the characteristic differences of seeds, their chemical constituents, their tegumentary coverings, rudimentary parts, etc., thoroughly understand the process in its outward manifestation. There is no precipitation of molecules as in an organic fluid, unless the albumen lying between the embryo and testa of the seeds, and constituting the nutriment on which the plant feeds during its primary stages of growth, can be called a fluid. It throws none of its characteristic ingredients downward any more than upward. ”

“ Clearly the transverse development of a stem is the correlative, partly of its function as a channel of circulation, and partly of its function as a mechanical support. That an axis may lift its attached leaves into the air, implies thickness and solidity proportionate to the mass of such leaves; and an increase of its sap-vessels, also proportionate to the mass of such leaves, is necessitated when the roots are all at one end and the leaves at the other. ”

“ Why since many seeds contain much oyl within them, they endure it not well without, either in their growth or production? Why since Seeds shoot commonly under ground, and out of the aire, those which are let fall in shallow glasses, upon the surface of the water, will sooner sprout then those at the bottom? And if the water be covered with oyle, those at the bottome will hardly sprout at all, we have not room to conjecture. ”

“ We see the seed shoot up into stem and leaf and throw out flowers; we observe it fulfilling processes of chemistry more subtle than were ever executed in Liebig's laboratory, and producing structures more cunning than man can imitate. ”

“ The branches of the stem or axis correspond for the most part in disposition with that of the leaves from the axils of which they originate, subject, however, to numerous disturbing causes, and to alterations from the usual or typical order brought about by the development of buds. These latter organs, as it seems, may be found in almost any situation, though their ordinary position is in the axil of a leaf or at the end of a stem or branch. ”

“ When the seed falls into the earth, which contains the right combination of heat and moisture, it swells and becomes porous, and, grasping the surrounding earth, attracts to itself all that is suitable for it and that has affinity to it. These particles of earth, however small they may be, as they fall and insinuate themselves into all the pores of the seed, broaden its bulk and make it send forth roots below, and shoot upwards, sending forth stalks no less numerous than the roots. ”

“ When the seed of any plant begins to grow, the first little shoot is so soft that you can mash it to a green paste between your fingers. Even a sprouting oak or maple is as soft as that. It has no bark. ”

“ The relatively rigid nature of the plant cell-wall, and the attenuated inorganic food-supply of plants, make possible and necessary a form of growth in which the greatest surface is exposed to the exterior, and thus the plant body is composed of flattened laminae and elongated branching growths. ”