Plant (biology)

“ The fact of outstanding importance to everyone who really looks at most plants is that part of them are above ground and part below. This simple observation carries with it the recognition of a fundamental difference of plant structure, namely roots and stem. Most plants bear obvious leaves, and at some time in their life flowers, inevitably followed by fruits and seeds. The ideally perfect plant would consist, then, of root, stem, leaves, flowers, fruit, and seed. ”

“ Flowers are the most exquisitely delicate in their texture of all forms in the vegetable kingdom. Look at the petals of this one. Could anything be softer or finer? The leaf, the bark, and the wood of the plant are all coarse, in comparison to the flower. Now, as nothing is made in vain, there must be some reason for this. The leaves and bark, as well as wood, of plants, all have vessels through which sap flows, and this sap nourishes, sustains, and builds up the plant, as our blood does our bodies. But the whole effort of the plant is to reproduce itself ”

“ The very simplest plants (if such may specifically be called plants rather than animals, or one may say, the simplest living things) are mere particles, or pellets, or threads, or even indefinite masses of protoplasm of vague form, which possess powers of motion or of changing their shape, of imbibing water, air, and even other matters, and of assimilating these into plant-stuff for their own growth and multiplication. Their growth is increase in substance by incorporation of that which they take in and assimilate. ”

“ 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. ”

“ When we reflect that the constant removal of water in the leaf, both as such, and as the only carrier of food supplies from the roots, depends in such large measure upon the functioning of these guard cells, then we come to some realization of their importance to the plant. ”

“ The fact that the largest tree and the smallest herb are alike made up of a greater or less number of these plant-members, as they are termed, leads naturally to the thought that any mass of plant-tissue having a root, a stem, and a leaf, may be a plant individual, and that, when a number of these members are intimately associated together, a community of plant individuals is formed. ”

“ When one takes up a plant his attention is naturally first drawn to its general appearance and structure, whether it is a complicated one like one of the flowering plants, or some humbler member of the vegetable kingdom,—a moss, seaweed, toadstool,—or even some still simpler plant like a mould, or the apparently structureless green scum that floats on a stagnant pond. ”

“ For, to continue the simile I have borrowed from the vegetable kingdom, is it not almost the same thing, whether we live successively to witness the germination, blooming, foliage, fecundity, fading, withering and corruption of a plant, or whether a vast number of specimens, selected from every stage through which the plant passes in the course of its existence, be brought at once to our view? ”

“ Actually what are ordinarily thought of as plants make up only a fraction of the great plant world. The fact that our familiar roadside and garden plants produce blossoms followed by a fruit and seed, such as peas and beans and all the ordinary flora of any region, separates them at once from that other large group of plants that do not. Common examples of the latter class are the green scum on the ponds, moss, seaweed, the rust on wheat, yeast, disease-causing bacteria, the smallest of all known plants, and many others. ”

“ Among plants, as distinguished generally from animals by the production and abundant use of chlorophyll and of cellulose, we have still existing on the Earth a range of forms extending from almost the most primitive organism that we can imagine up to the splendid Seed Plant, specialized in a hundred ways. ”

“ It learned to divide the work of the plant by making organs—roots, stems, leaves, blossoms, fruits. The lowest plant is a cell, but the highest is only a multitude of cells made of the one material—protoplasm, but changed into many forms and given many kinds of work to do. From using water alone to float in, the plant learned to use earth, air, wind, insects, birds and men, to help it make and scatter its seeds, and to grow better plants. ”

“ But though it is fairly easy to see how the plant cells form one from another, that does not explain how they come to make a plant, with its many different parts, with its root and stem, its branches, leaves, and flowers. ”

“ We find all through the plant-world that the structure of a plant depends very much on the kind of conditions under which it is living, and in the case of those growing in the water, it is [161] quite clear how the soft, air-filled stems are one result of their mode of life, and are well adapted to it. ”

“ It must be remembered that botany does not consist in collecting, drying, and drawing plants alone, but it relates to everything about the vegetable kingdom of nature. The growth of the plant from the seed; how it lives, breathes, and its sap circulates ”

“ The latter, when duly fertilized by being brought into contact with the "pollen" of the stamens, become "seeds," and are capable of growing up, when planted, into new plants. Now, the botanist will inform us that it is a matter of common experience to find some individual plants of a species with well-developed petals or blossoms, and other individuals of the same species with petals in a rudimentary condition, thus proving that the production of imperfect parts in flowers occurs as an ordinary event under our own eyes, and under the common conditions of plant-life. ”

“ From the architecture of their outer characteristics, which takes up the first chapter, we have gone step by step into the story of what goes on within the plant, and how it reproduces its kind. These actions or behavior of plants have resulted in many things of great practical importance as well as being of absorbing interest in themselves. What some of these results have been, we see reflected in the uses of plants to man, in the history of their development, and, most of all, in the way they are distributed over the earth to-day. ”

“ At a certain period in the life both of plants and animals, varying according to their kind and the [Pg 37] climate they live in, they are fit for and disposed to the reproduction of their species. The sexes in both are then attracted to each other. In plants, the powder termed pollen, in animals a peculiar liquid which, deriving its name by analogy from the seeds of plants, is termed seminal, is secreted by the male plant or animal, and, by organs differently formed in each kind, is cast upon ova or eggs either contained within, or deposited by, the female. ”

“ A single potato placed in the ground becomes a dozen or more, by a process of multiplying. A little seed planted in the earth grows up to be a plant, produces flowers, and from the flowers come other seeds, not one, but often a great many, sometimes hundreds from a single seed. Insects, fishes, birds, and all other animals, thus multiply. So do human beings, and in a similar manner. The organs by which this most marvelous process is carried on in plants and animals, including also human beings, are called sexual organs. Flowers are the sexual organs of plants. ”

“ They breathe when the leaf mouths take from the air the oxygen, and give back to it carbonic-acid gas.
The veins and veinlets, of which you see so many running through a leaf, act in something the same way as the water pipes of a city; for through these veins the watery food, the earth broth, is carried to the different cells.
When one knows all that we know even now about a plant, one looks at a tree covered with leaves with a good deal of admiration. ”

“ These factors are physical, or chemical, or biological, and affect the plant mainly through the agency of the soil, the atmosphere, or living organisms.
“The living plant is a synthetic machine.” Under proper working conditions of heat, moisture, and light it builds up its body by absorption of inorganic{99} material, liquid and gaseous, through its roots and leaves. ”

“ Form, color, the secretion of sweetish nectar, the night or day blooming of different kinds of flowers, every device that will make fertilization certain, by the flower itself, by insects, or even by the wind, is used in such prodigal fashion, that we come to see the importance of it to all plants only by a realization of the complexity of it and the provisions against its failure. ”

“ 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. ”

“ The most prominent of these parts are root, stem, leaf, flower, fruit, and seed. Familiar plants differ wonderfully in size and shape,—from fragile mushrooms, delicate waterweeds and pond-scums, to floating leaves, soft grasses, coarse weeds, tall bushes, slender climbers, gigantic trees, and hanging moss.
The Stem Part.—In most plants there is a main central part or shaft on which the other or secondary parts are borne. This main part is the plant axis. Above ground, in most plants, the main plant axis bears the branches, leaves, and flowers; below ground, it bears the roots. ”

“ Only the gross anatomy of the plant is considered and the ordinary routine of beginning with the simpler forms and advancing to ones of successively more complex structure is followed, and the principles of reproduction and physiology are presented. The student is given an insight into the adaptive processes of the plant by a study of the special forms which live in the water, dry soil, deserts, and other special conditions. ”

“ The growth of plant-life, which runs concurrently with the changing seasons of the year, impresses this fact upon us, and the history of animal development but repeats the tale. From seed to seed-leaf, from seed-leaf to stem and leaves, from simple leaves to flower, and from flower to fruit, there is exhibited a natural progress in plant-existence, which testifies eloquently enough, by analogy at least, to the existence of like tendencies in all other forms of life. ”

“ Biological science of our day takes it for granted that the process uniting pollen with seed in the plant is an act of fertilization analogous to that which occurs among the higher organisms of nature. ”

“ But the whole plant, often many feet in length, consists only of single gigantic cells. A tough skin incloses its juices, which flow in a continuous stream through the stem, leaves, and roots of the curious growth, here taking up through the skin and assimilating mineral substances, there producing and transforming organic matter, and at the same time advancing the growth and increase of the whole. Not less peculiar than the inner structure and appearance of the stem is the form of the leaves of water plants. Their service to the organism is the same with that of the leaves of other plants. ”

“ When studying woods we must consider the width of the medullary rays, the structure and cell contents of the medullary ray cells; the structure, color, and cell contents of the wood parenchyma; also the wood fibres.
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CHAPTER VI
LEAVES
Leaves collectively constitute the greatest manufacturing plant in the world. Most of the food, clothing, and medicine used by man is formed as a result of the work of the leaf. ”

“ It has been already observed that the life of the plant consists chiefly in the formation of its organs; whence it follows, that its most essential and fundamental activity manifests itself in the process of assimilation and secretion, as well as in the circulation of the sap, which is nothing but a repetition of the chemical attraction and repulsion observed in unorganized matter. ”

“ They never grow into branches, but detach themselves when full grown, fall to the ground, and take root there to form new plants.
Fig. 110. Bulblets in the axils of leaves of a Tiger Lily.
117. Consolidated Vegetation. An ordinary herb, shrub, or tree is evidently constructed on the plan developing an extensive surface. In fleshy rootstocks, tubers, corms, and bulbs, the more enduring portion of the plant is concentrated, and reduced for the time of struggle (as against drought, heat, or cold) to a small amount of exposed surface, and this mostly sheltered in the soil. ”

“ The chapters on the families of plants attempt to bring out the reasons for the separations of the few great groups only; detailed classification of the flowering plants has so long been considered the chief part of botany, that it is to be found in nearly every schoolbook on the subject. ”