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and rearranged them as little as possible, preferring the certainty of leaving them in an inartificial state to the risk of spoiling by manipulation whatever value they may possess as records made at the time.Mind.
THE ORIGIN OF FRUITS.
BY PROFESSOR GRANT ALLEN.
lovelier than flowers; but the second rank in beauty may be fairly claimed on behalf of fruits. Whether we look at the golden oranges, the pink-cheeked mangoes, the purple star-apples, and the scarlet capsicums of the south, or at our own crimson cherries, blushing grapes, bright holly-berries, and rosy apples, we are equally struck with the delicacy of their melting tints and the graceful curves of their rounded form. Our painters have reveled in their rich coloring ; and even our sculptors, whose fastidious art compels them to reject that meretricious charm, have loved to chisel their swelling contours in snowy stone. As they hang pendent from their native boughs, clustering in brilliant masses, or scattered here and there as points of brighter light amid the dark foliage which throws up in strong relief their exquisite hues, we may recognize in their beauty the ultimate source of all that refined pleasure which mankind derives from the varied shades of earth and sea and sky, of flower and bird and butterfly, and even of the “human face divine” itself. From the contemplation of ruddy or snowy berries in primeval forests the frugivorous ancestors of our race first acquired the taste for brilliant hues, whose final outcome has produced at length our modern picture-galleries and palaces, our flower-gardens and conservatories, our household ornament and our decorative art.
In a previous paper on “The Origin of Flowers," we endeavored to trace the mutual reactions of insects and blossoms upon one another's forms and hues. But we then deferred for a while the consideration of the further question-“Why do human beings admire these bright whorls of colored leaves, whose primitive function consisted in the attraction of bees and butterflies ? Through what community of origin or nature does the eye of man find itself agreeably stimulated by the tints which were first developed to suit the myriad facets of primeval insects ?" The answer to this question we have now to attempt, by showing the various steps through which the coverings of certain seeds acquired, for the vertebrate orders—the birds and quadrupeds-exactly the same allurements of color, scent, and taste, which flowers had already acquired for the articulate orders--the bees and butterflies.
* See POPULAR SCIENCE MONTHLY SUPPLEMENT, No. XIV., p. 151.
To the attractive hues of fruit, I believe, we must ultimately trace back our whole artistic pleasure in the pure physical stimulation of beautiful colors, displayed by natural objects or artificial products.
Our present inquiry, then, will yield us some account of that primitive delight in red, purple, orange, and yellow, which we usually take for granted as an innate instinct of humanity, savage or civilized. When, some few months back, we analyzed the various elements of pleasure which make up our ästhetic enjoyment of a daisy, we were compelled, for the time being, to leave the original beauty of its pinkand-white rays wholly unexplained. We regarded the delight in color, relatively to the subject we were then examining, as an ultimate and indecomposable factor in our developed consciousness. To-day, however, I hope we shall be able to go a little further back, and to show that this delight, like all other feelings of our nature, is no mere chance and meaningless accident, but the slow result of a long adaptation whereby man has gradually become fitted to the high and responsible station which he now occupies at the head of organic existence.
The sole object of flowering is the production of seeds—that is to say, of embryo plants, destined to replace their parents, and continue the life of their species to future generations. Flowers and seeds go together; every flower producing seed, and every seed springing from a flower. Ferns and other like plants, which have no blossoms, bring forth spores which grow into shapeless little fronds, instead of true seeds containing a young plantlet. But all flowering species produce some kind of genuine fruit, supplied with more or less nutriment for the tender embryo in its earlier days. And this matter of nutriment is so important to a right comprehension of our subject that I venture, even at the imminent peril of appearing dull, to digress a little into the terrible mysteries of Energy, which comprise the whole difficulty of the question.
Wherever movement is taking place in any terrestrial object, the energy which moves it has been directly or indirectly supplied from the sun. In the green parts of plants, the solar rays are perpetually producing a separation of carbon and oxygen, the former element being stored up in the tissues themselves, while the latter is turned loose upon the atmosphere in a free state. Whenever they recombine, motion and heat will result, as we see alike in our grates, our steamengines, and our own bodies. An animal is a sort of machine-viewed from a purely physical standpoint-in which the energetic materials laid up by plants are being reconverted into the warmth which reveals itself to our touch, and the evident movement which we see in its limbs. The vegetable or animal substances which are capable of yielding these energies to our bodies we know as food or nutriment. They perform exactly the same part in the physical economy of men or beasts as that which fuel performs in the physical economy of the steam-engine. Of course, from the mental point of view, we have the
immense difference between a self-conscious, self-guiding organism, and a dead machine requiring to be supplied and regulated by an external consciousness ; yet in the fundamental physical necessity for energetic material, either as food or as fuel, both mechanisms follow essentially the self-same mechanical laws.
But what has all this to do with the origin of fruits ?. Very little at first sight, indeed, yet everything when we look at the bottom of the question. In fact, what is thus true of animals and steam-engines is equally true of plants. No motion can take place in a growing shoot without the aid of solar energy, directly supplied by the sunshine, or indirectly laid by in the older tissues. In the green parts of a plant this energy is immediately derived from the bounteous light which bathes and vivifies the leaves on every side ; but in many other portions of the vegetable organism, energies previously accumulated by older organs are perpetually being utilized, for the production of movement and growth, by lazy structures which cannot work for themselves, and so feed upon the useful materials collected for them by more industrious members of the plant-commonwealth. Especially is this the case with those expensive organs which are concerned in perpetuating the species to future generations. A flower or a seed cannot directly transform waves of light into chemical separation of atoms; they depend for their growth and the due performance of their important functions upon similar separations already carried on for their behoof by the green leaves on whose bounty they rely for proper subsistence. Carbon, set free from oxygen in the leaves, has been carried to them in loose combinations by the sap; and as the bud unfolds or the seed germinates, the oxygen once more unites with this carbon (just as it unites in the furnace of the steam-engine, or the recesses of the animal body), and motion is thereby rendered possible. But without such an access of free oxygen to recombine with the energetic materials, the blossom or the embryo could never grow at all. So we may regard these portions of a plant, incapable of self-support, and dependent for their due function upon energetic compounds laid by elsewhere, as the exact analogues of the animal or the steam-engine. They are in fact similar mechanisms, where food is being used up, and fuel is being consumed ; and we find accordingly, as we might naturally expect, not only that motion results, but also that heat is evolved in quantities quite sufficient to be measured by very delicate thermometers.
Now, every growing portion of a plant shares, more or less, in this animal function of feeding upon previously-fabricated nutriment. But there are two sets of organs, both intended ultimately to subserve the same purpose, in which that function becomes especially apparent. The first is in the case of the whole regular reproductive mechanism, including in that term buds, flowers, fruits, and seeds; the second is in the case of such subsidiary reproductive devices as tubers, rhizomes, corms, and all the other varieties of underground stems or roots, which
botanists divide into so many puzzling technical classes, while ordinary people are content to lump them roughly together as bulbs. If we glance briefly at each of these two cases, we shall be able to comprehend more fully their connection with the doctrine of energy, and also to see more clearly the problem before us when we endeavor to unravel the origin of fruits.
A germinating pea or a young blade of wheat is supplied by its parent with a large stock of nutriment in the shape of starch, albumen, or other common food-stuffs. If we were to burn the wheat instead of planting it, the energy contained in its substance would be given off during the act of combustion as light and heat. If, again, we were to adopt a more usual course, by grinding, baking, and eating it, then the inclosed energy would minister to the warmth of our bodies, and do its little part in enabling us to walk a mile or to lift a heavy weight. 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. By the time that all the stored-up nutriment contained in the seed has been thus devoured by the young plantlet, these
surfaces are in a position to assimilate fresh material for themselves, from the air which bathes them on every side, under the energetic influence of the sunbeams that fall each moment on their growing cells. But I need hardly point out the exact analogy which we thus perceive between the earliest action of the young plant and the similar actions of the frugivorous animals which subsist upon the food intended for its use.
If, however, we look at the second great case, that of bulbs and tubers, we shall see the same truth still more clearly displayed. You cannot grow a blade of wheat or a sprouting pea in the dark. The seed will germinate, it is true ; but, as soon as the primitive store of nutriment has been used up, it will wither away and die. Naturally enough, when all its original energy is gone, and no new energy is afforded to it from without in the form of sunshine, it cannot miraculously make growth for itself out of nothing. But if you put a hyacinthbulb in a dark cellar, and supply it with a sufficiency of water, it will grow and blossom almost as luxuriantly as in a sunny window. Now, what is the difference between these two cases ? Simply this: the wheat-grain or the pea has only nutriment enough supplied it by the parent-plant to carry it over the first few days of its life, until it can shift for itself; while the hyacinth has energetic materials stored up in its capacious bulb to keep it in plenty during all the days of its summer existence. If we plant it in an open spot where it can bask in the bright sunshine, it will produce healthy green leaves, which help it to flower and to carry on its other physiological actions without depending entirely upon its previous accumulations ; but if we place it in some dark corner, away from the sun, though its leaves will be blanched and sickly-looking, it will still have sufficient nutriment of its own to support it through the blossoming season without the external aid of fresh sunshine.
Where did this nutriment come from, however? It was stored up, in the case of the seed, by the mother-plant; in the case of the bulb, by the hyacinth itself. The materials produced in the leaves were transferred by the sap into the flower or the stem, and were there laid by in safety till a need arose for their expenditure. All last year-perhaps for many years before—the hyacinth-leaves were busily engaged in assimilating nutritive matter from the air about them, none of which the plant was then permitted to employ in the production of a blossom, but all was prudently treasured up by the gardener's care in the swelling bulb. This year, enough nourishment has been laid by to meet the cost of flowering, and so our hyacinth is enabled to produce, through its own resources, without further aid from the sun, its magnificent head of bright-colored and heavily-scented purple bells.
Each species of plant must, of course, solve for itself the problem, during the course of its development, whether its energies will be best employed by hoarding nutriment for its own future use in bulbs and tubers, or by producing richly-endowed seeds which will give its offspring a better chance of rooting themselves comfortably, and so surviving in safety amid the ceaseless competition of rival species. The various cereals, such as wheat, barley, rye, and oats, have found it most convenient to grow afresh with each season, and to supply their embryos with an abundant store of food for their sustenance during the infant stage of plant-life. Their example has been followed by peas and other pulses, by the wide class of nuts, and by the majority of garden-fruits. On the other hand, the onion and the tiger-lily store nutriment for themselves in the underground stem, surrounded by a mass of overlapping or closely-wound leaves, which we call a bulb; the iris and the crocus lay by their stock of food in a woody or fleshy stalk ; the potato makes a rich deposit of starch in its subterraneous branches or tubers; the turnip, carrot, radish, and beet, use their root as the storehouse for their hoarded food-stuffs ; while the orchis produces each year a new tubercle by the side of its existing root, and this second tubercle becomes in turn the parent of the next year's flowering stem. Perhaps, however, the common colchicum or meadow-saffron affords the most instructive instance of all; for during the summer it sends up green leaves alone, which devote their entire time to the accumulation of food-stuffs in a corm at their side; and, when the autumn comes round, this corm produces, not leaves, but a naked flower-stalk, which pushes its way through the moist earth, and stands solitary before the October winds,