In these six steps Nature continually completes her endless work of the propagation of plants by the two sexes.

CHAPTER X

THE FRUITS

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It is now the fruit which we have to observe, and we shall soon be convinced that this too originates in the same way as the previous parts and is subject to the same laws. We speak here really of those vessels or capsules formed by Nature to enclose the so-called covered seeds, or rather to develop through fructification within these vessels a greater or lesser number of seeds. It will be easy to show that these vessels may likewise be explained according to the nature and organisation of those parts of the plant we have already considered.

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It is once more the retrogressive metamorphosis which brings to our notice this law of Nature. We may often observe in pinks, for example—which just because of this irregularity are such well-known and favourite flowers—that the seed capsules transform again into leaves like those of the calyx, and that in just the same proportion the styles become shorter. Indeed, it even happens sometimes that the fruit capsule of a pink transforms into a real and perfect calyx, the divisions of which still have tender remnants of styles and stigmas attached to them, while from the very centre of this second calyx a more or less perfect corolla develops instead of seeds.

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Furthermore even in normal and constant formations Nature reveals in manifold ways the fruitfulness that lies hidden in the leaf. Thus a leaf of the lime—a somewhat changed leaf, it is true, but none the less quite recognisably a leaf—produces from its middle vein a little stalk and on it a perfect blossom and fruit. In Ruscus this manner in which the blossom and fruit rest on the leaf is still more remarkable.

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Still greater—we may even say monstrous—is this inherent fruitfulness of the leaf as shown to us in ferns. Through an inner impulse, and perhaps even without the direct operation of two sexes, they develop and scatter around innumerable seeds, or tiny germs, capable of growth, so that a single frond rivals a wide-spreading plant in fruitfulness, or even a large branching tree.

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If we keep observations in mind we shall not fail to recognise the leaf-form in all seed-vessels, in spite of their manifold formations, their peculiar modifications and combinations. So for example, many pods may be regarded as a single leaf, folded and grown together again at the edges; others again consist of several leaves grown one upon another; compound pods or capsules may be explained as composed by several leaves united around a common centre, joined at their edges but open towards one another on their inner sides. We are convinced of this even by visual demonstration when such capsules, having become set together, burst apart after the ripening of the seed, so that each part shows itself to be an open pod or shuck. We also see, in various types of one and the same species, a similar process taking place normally; for example, the fruit capsules of Nigella orientalis are formed of pods partly grown together and collected round an axis, while in Nigella damascena they are completely united.

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Nature conceals this likeness to the leaf-form most when she forms soft and juicy or hard and woody seed-vessels. But even then it will not escape our notice if we know how to follow this development carefully through all its transitions. Here it is enough to have indicated the general idea and to have shown by means of a few examples Nature's unity of purpose. The manifold varieties of seed-capsules will afford us material for future and further consideration.

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The relation of seed-vessels to the preceding parts is also made apparent in the stigma, which in many cases sits immediately upon the ovary and is inseparably united with it. We have already shown the relation of the stigma to the leaf-form and can mention it once again as it may be seen in double poppies, where the stigmas of the seed-capsules are changed into delicate coloured petals—quite true leaf-forms.

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The last and greatest expansion effected by the plant in the course of its growth comes to expression in the fruit. It is often great, even monstrous, both in internal strength and external form. As it usually grows bigger after fertilisation it would seem that the now more fully determined seed that is to be, while drawing the juices needed for its growth from all parts of the plant, directs them mainly to the seed-covering— or fruit—whereby the vessels of the latter are nourished, enlarged and often to a very great extent filled out and distended. It may be inferred from what has already been said that purer forms of air have had a great share in this, and experiment has shown that the swollen pods of Colutea contain pure air.

CHAPTER XI

THE IMMEDIATE COVERING OF THE SEED

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On the other hand we find in the seed itself the highest degree of contraction and inner perfection. It may often be observed that the seed transforms leaves into its immediate covering, adapting them more or less to its shape and indeed usually having the power to attach them fast to itself, entirely changing their form. Having already seen that many seeds may develop from and within a single leaf, we shall not wonder that a single embryo should clothe itself in a leaf covering.

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We see in many winged seeds traces of such leaf-forms not perfectly fitted to the seed— for example, the maple, the elm, the ash and the birch. A very remarkable example of the way in which the rudimentary seed gradually draws together wider coverings and adapts them to its own size is given to us us by the pot marigold, with its three circles of differently formed seeds. The outermost circle retains a form related to the leaflets of the involucre, except that a rudimentary seed, causing the vein to buldge, makes the leaf curved; the inner side of this curved surface is then divided along its length into two parts by a membrane. The next circle has become even more changed; the width of the leaf and the membrane have quite disappeared; on the other hand the form has lengthened to a lesser degree and the rudimentary seed is more plainly visible at the back, the little mounds more defined. Both of these rows seem either not at all or only imperfectly fructified. Then follows the third circle of seeds, in their true form—very rounded and with a completely fitting covering, fully developed with all its little mounds and ridges. We see once more the powerful contraction of expanded leaf-like parts, brought about moreover through the inner power of the seed just as before we saw the petal contracted through the power of the anther.

CHAPTER XII

A GLANCE BACKWARD AND FORWARD

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So we have followed Nature's footsteps as thoughtfully as may be: we have traced the outward form of the plant in all its transformations—from the development out of the seed until the seed is formed once more—and, without wishing in arrogance to probe the hidden springs of impulse in Nature's operations, we have directed our attention to the outward manifestations of those powers through which the plant, step by step, transmutes one and the same organ. In order not to abandon the thread once taken up, we have all the time been considering only annual plants. We have simply observed the transformation of the leaves which accompany the nodes and from them have deduced all varieties of form. All that now remains to be done, in order to give this attempt its necessary completeness, is to speak of the eyes which lie hidden beneath each leaf and develop under certain circumstances while under others they seem completely to disappear.

CHAPTER XIII

EYES AND THEIR DEVELOPMENT

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Every node has by nature the power to produce one or more eyes. They appear close to the accompanying leaves, which seem to prepare and to help their formation and growth.

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On the successive development of one node out of another and on the formation of a leaf at every node and an eye close by it, rests the first simple, slow process of growth by which vegetable life is propagated.

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It is well known that such an eye is very like a ripe seed in its working, and that often in the eye, more easily than in the seed, the entire form of the future plant may be recognised.

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Even though the point at which the root will be developed is not so easily detected in the eye, yet it is there, just as it is in the seed, and develops quickly and easily, especially under the influence of moisture.

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The eye does not need cotyledons, because it is connected with the parent plant which, now completely organised, provides sufficient nourishment as long as this connection lasts.