Metamorphosis of Plants

 Johann Wolfgang von Goethe

Sourced From Johann Wolfgang von Goethe’s “Scientific Studies“

 

INTRODUCTION

Anyone who observes even a little the growth of plants will easily discover that certain of their external parts sometimes undergo a change and assume, either entirely, or in a greater or lesser degree, the form of the parts adjacent to them.

So the simple flower, for example, often changes into a double one, if petals develop in the place of stamens and anthers. These petals may either perfectly resemble the other petals of the corolla both in form and colour, or they may still retain visible signs of their origin.

If we see that in this way it is possible for the plant to make a retrograde step and reverse the order of growth, we shall become all the more aware of the normal course of Nature, and shall learn to understand those laws of transformation by which she produces one part out of another and creates the most varied forms by the modification of one single organ.

The secret affinity between the various external parts of the plants, such as leaves, calyx, corolla and stamens, which are developed one after the other and as it were one out of the other, has long been recognised in a general way by naturalists; indeed, much attention has been given to the study of it. The process by which one and the same organ presents itself to us in manifold forms has been called the metamorphosis of plants. There are three kinds of metamorphosis: regular, irregular and accidental.

Regular metamorphosis we may also call progressive, for here we may follow the development step by step from the first seed-leaves to the final forming of the fruit, ascending through transformations of one form into another, as by a spiritual ladder, to that crowning aim of Nature, the propagation of the plant by male and female organs. I have been attentively observing this process for some years, and it is in order to explain it that I am writing now. In the following demonstration we shall therefore study the plant only in so far as it is annual and proceeds without pause from the seed to fertilisation.

Irregular metamorphosis may also be called retrogressive. For as in the former case Nature hastens forward to her great aim, here she takes one or more steps backward. In the former instance, with irrestible impulse and powerful effort she forms the flowers and fits them for the service of love; in the latter she seems as it were to relax, and irresolutely leaves her creation in an indefinite and soft state, often pleasing to the eye, but intrinsically powerless and inactive. Frequent experience of this kind of metamorphosis will enable us to disclose what in the regular way of development is hidden from us, and to see clearly and visibly what we should otherwise only be able to infer. In this way we may hope to attain our purpose with the greatest possible certainty.

The third kind of metamorphosis, on the other hand, which is brought about accidentally by external causes, and especially by insects, we shall not take into consideration; it might lead us astray from the simple path we have to follow and delay the attainment of our object. Perhaps an opportunity will be found elsewhere to speak of these growths; monstrous they are, yet confined within certain limits.

I have ventured to publish this attempt without explanatory illustrations necessary as they might seem in some respects. I may introduce them later; this can easily be done as sufficient material still remains for elucidating and enlarging this short and preliminary treatise. It will not then be necessary to keep so measured a step as now. I shall be able to produce much that relates to the subject, and numerous quotations from authors holding similar views will appear in their right place. Above all I shall not fail to make use of observations gathered from those contemporary masters of whom this science can boast. To them I present and dedicate these pages.

CHAPTER I
OF THE SEED-LEAVES

As we have set out to observe the successive steps in the growth of the plant we will begin by directing our attention to it when first it develops out of the seed. At this stage the parts which directly belong to it are easily and exactly distinguishable. It leaves its sheathes more or less behind in the earth; these we will not examine now. Then in many cases, when the root has fastened itself in the soil, the plant brings to the light the first organs of its upper growth, which were already there, hidden under the seed-coat.

These first organs are known as cotyledons; they have also been called seed valves, kernel pieces, seed-lobes, or seed-leaves, in the attempt to name them according to the different forms in which we find them.

They often appear unshapely, stuffed as it were with a crude substance and distended as much in thickness as in width. Their vessels are unrecognisable and scarcely to be distinguished from the mass of the whole, and they have hardly any resemblance to a leaf, so that we might be misled into believing them to be special organs.

Yet in many plants they approach the shape of a leaf; they become flatter, and when exposed to light and air they assume a deeper green, and the vessels contained in them become more recognisable, more like leaf-veins.

Finally they sometimes even take on the appearance of real leaves. Their vessels are then capable of high development, and their resemblance to the subsequent leaves does not permit us to regard them as distinct organs; we have to recognise them as the first leaves of the stem.

Now as we cannot conceive of a leaf without a node or of a node without an eye, we may conclude that the point at which the cotyledons are attached is the first true node of the plant. This view is confirmed by those plants which produce young eyes immediately under the wings of the cotyledons, and from these first nodes develop complete branches, as, for example, is the case with the common bean, Vicia Faba.

The cotyledons are usually double; and here we have a remark to make which will appear to us of still greater importance later on. Namely, the leaves of this first node often appear in pairs, even when the subsequent leaves of the stem are placed alternately. Here then is shown a coming together and uniting of parts which Nature later separates and places at a distance one from the other. Still more remarkable is it when the cotyledons appear like many little leaves gathered round a single axis, while the stem which gradually develops out of their midst produces the subsequent leaves singly around itself. This may be very well observed in the growth of the different kinds of pine; where a wreath of needles forms as it were a calix. As we proceed we shall be reminded of this in other similar phenomena.

For the present we will pass over the quite shapeless single cotyledons of plants which germinate with one leaf only.

Let us remark, however, that even the most leaf-like cotyledons, in comparison with the subsequent leaves of the stem, are always less developed. Above all their margin is extremely simple, with as few traces of incisions in it as there are of hairs on the surface, or of any of those vessels which are to be observed in perfect leaves.

CHAPTER II
THE DEVELOPMENT OF THE STEM-LEAVES FROM NODE TO NODE

We are now able to observe closely the successive formation of the leaves, as the progressive operations of Nature all take place before our eyes. Some, or many, of the leaves which now appear are often already present in the seed and lie enclosed between the cotyledons; in their folded state they are called plumules or “little feathers.” Their shape, compared with that of the cotyledons and of the future leaves, varies in different plants, but they usually differ from the cotyledons in that they are flat, delicate and formed altogether like real leaves; they become entirely green, they are attached to a visible node and their relation to the following stem-leaves can no longer be denied. They are, nevertheless, inferior to them in so far as their periphery or margin is not yet perfectly formed.

Henceforward the further development of the leaf progresses without pause from node to node; the vein lengthens out and the veins that branch out from it extend more or less towards the edge. These different relationships of the veins to one another are the primary cause of the manifold leaf-shapes. The leaves may appear notched, deeply-incised, or formed of many leaflets joined together, in which case they resemble perfect little twigs. The date palm affords a striking example of the simplest type of leaf developing into the most manifold forms. As the leaves succeed each other the central vein grows more and more prominent, the fan-like and yet simple leaf becomes torn and divided and an extremely compound, branchlike leaf is formed.

The development of the leaf-stalk keeps pace with that of the leaf. The two are either intimately connected or the stalk forms a special little stem which at long last is quite easily detached from the leaf as such.

That this independent leaf-stalk also has a tendency to change into the form of a leaf, is disclosed by a variety of plants, the Agrumae for example. The organization of the leaf-stalk, which for the present we will pass over, will prompt us to further considerations in the future.

Neither can we for the moment enter upon a closer examination of bracts and stipules. We can only observe in passing that, especially when they constitute a part of the leafstalk, they share its future transformations in many remarkable ways.

While the leaves owe their first nourishment principally to the more or less modified watery parts which they draw from the stem, for their increased perfection and refinement they are indebted to the light and air. The cotyledons which are formed beneath the closed seed-sheath are charged, so to speak, with only a crude sap, they are scarcely or but rudely organised and quite undeveloped. In the same way the leaves are more rudely organised in plants which grow under water than in others which are exposed to the open air. Indeed, even the same species of plant develops smoother and less intricately formed leaves when growing in low damp places, while, if transplanted to a higher region, it will produce leaves which are rough, hairy and more delicately finished.

So also the anastomosis of the vessels which spring forth from the larger veins, seeking each other with their ends and coalescing, and thus providing the necessary basis for the leaf-skin or cuticle, if not entirely caused by subtle forms of air, is at least very much furthered by them. If the leaves of many water-plants are thread-like or assume the form of antlers we are inclined to attribute it to a lack of complete anastomosis. The growth of the water buttercup, Ranunculus aquaticus, shows us this quite obviously, with its aquatic leaves consisting of mere thread-like veins, while in the leaves developed above water the anastomosis is complete and a connected plane is formed. Indeed, occasionally in this plant, the transition may be still more definitely observed, in leaves which are half anastomosed and half thread-like.

Experience has taught that the leaves draw in various kinds of air which they combine with the moisture contained within them, and there is no doubt that they bring these more refined juices back again into the stem, and so greatly promote the development of the adjacent eyes. This has been ascertained by examining the kinds of air developed in the leaves of many plants, and even in the cavities of hollow stems.

We observe in many plants that one node spring from the other. In the stems of the cereals, grasses and reeds, which are closed from node to node, this is obvious; but it is not so obvious in plants whose centre is hollow throughout or filled with pith, that is, with loose cellular tissue. But the supposed important functions of the pith or “marrow” being now on good ground called into question, and the impulsive and productive power once claimed for it being today attributed to the inner side of the second rind, the so-called cambium, we can now more easily understand that a more highly situated node, developing as it does from a preceding one and receiving the juices from it in a finer and more highly filtered condition, benefits from the operation of the intervening leaves and will therefore develop all the more perfectly and in its turn transmit more elaborated juices to its own leaves and eyes.

In so far as the fluids are in this way constantly drained away and purer ones introduced, and the plant gradually develops into a more perfect condition, it attains the end ascribed to it by Nature. At length we see the leaves perfectly developed in size and form, and soon become aware of a fresh phenomenon, which tells us that the period we have observed so far is over, and that a second one is approaching, namely that of the flower.

CHAPTER III
TRANSITION TO THE FLOWER

The transition to the flowering condition takes place with greater or lesser rapidity. In the latter case we shall usually notice that the stem-leaves begin to contract once more from the periphery inward, and especially to lose their manifold outer incisions. On the other hand, they tend to spread out more or less where with their lower parts they are attached to the stem. At the same time we see that the spaces between the nodes of the stem become, if not perceptibly longer, at least more slender and more delicately formed in comparison with the preceding state.

It has been observed that copious nourishment hinders the flowering of a plant, while moderate or even scanty nourishment accelerates it. In this we see still more clearly the function of the stem-leaves which we have already been considering. As long as there are cruder juices to be drained away, the plant must continue to develop the necessary organs to carry out this task. If superfluous nourishment is forced on the plant, this task must be continued, and flowering becomes almost impossible. But if excessive nourishment is withheld, Nature’s operation is rather hastened and facilitated, the organs of the nodes become more refined, the unadulterated juices act more purely and more strongly. In a word, the metamorphosis of parts is made possible and takes place without delay.

CHAPTER IV
FORMATION OF THE CALYX

We often see this change taking place quickly; when this is so the stem shoots upward all at once from the node of the last developed leaf and becomes tapering and more delicate, ending in a little collection of leaves around an axis.

There seems to us to be quite clear proof that the leaves of the calyx are the same organs as those which we have so far seen developing into stem-leaves, only now they are collected—often in a very changed form—round a common centre.

We have already noticed a similar operation of Nature in the cotyledons, where several leaves—nay more, obviously several nodes—are gathered close to one another round a single point. The pine species in their development from the seed show a rayed circle of unmistakable needles which, in comparison with other cotyledons, are highly developed. When this plant is still quite young we can already see an indication, as it were, of that force of Nature which at a more advanced age will produce the blossom and fruit.

Furthermore, in many flowers we see unaltered stem-leaves collected together so as to form a kind of calyx just below the flower. As their form is still quite unchanged we can recognise that they are leaves by their appearance, and indeed in the botanical terminology they are called “flower leaves”—folia floralia.

With great attention we must watch the procedure in the case already mentioned when the transition to the flowering period takes place slowly; the stem-leaves gradually draw together, become modified and pass almost unawares into calyx-leaves. This may readily be seen in the compositae, especially in sunflowers and marigolds.

This force of Nature which collects a number of leaves around a single axis can bring about a still more intimate union, making the clustered and modified leaves more than ever difficult to recognise. The calyx-leaves or sepals are then joined together—either entirely so, or only partly grown together at the edges. These leaves, crowded and closely pressed to one another, touch most intimately while in their tender state. They become anastomosed under the influence of the very pure juices now present in the plant, and form the bell-shaped or so-called one leaved calyces revealing their composite origin by the way in which they are more or less incised or divided. We shall learn this if we compare a number of deeply incised single calyces with many-leaved ones and especially if we observe the calyces or involucres of some compositæ. Thus, for example, we shall see that the calyx of a marigold, which is defined in systematic descriptions as “simple and much-divided,” consists of several leaves grown into and over one another, into which, as we have already said, the contracted stem-leaves imperceptibly pass over.

In many plants the number and form in which the calyx-leaves or sepals, whether single or grown together, are arranged around the axis of the stalk, is constant, and this is also the case with the other subsequent parts. On this constancy rests to a great extent the progress, certainty and reputation of botanical science, which in recent years has been making continual advances. In other plants, the number and formation of these parts is not so constant, yet even this inconstancy has not escaped the keen powers of observation of the masters of this science; on the contrary, they have tried, by means of exact definitions, to restrict even this variation of Nature, as it were into some pattern of conformity.

Thus has Nature formed the calyx, by uniting—around a common centre, and as a rule in definite number and order—many leaves and consequently many nodes which she would otherwise have produced one after the other and at some distance apart. If the flowering period had been retarded by the in-streaming of superfluous nourishment, the nodes and leaves would have appeared separated from one another in their original form. Nature, therefore, in forming the calyx creates no new organ, but simply combines and modifies the organs we already know, advancing in this way a step nearer her goal.

CHAPTER V
FORMATION OF THE COROLLA

We have seen how the calyx is produced through the influence of refined juices gradually generated in the plant, and now the calyx itself is destined to become the organ of a future and further degree of refinement. We can believe this even if we explain its operation from a purely mechanical point of view. How tender and capable of the finest filtration must be the vessels which are so highly contracted and drawn together!

The transition from the calyx to the corolla can be seen quite clearly, for although the calyx is usually green like the stem-leaves, it often shows a change in one part or another at the tips, the edges, the back or even over the inner surface, leaving the outer surface green. Also whenever this colouring occurs we see it combined with an increased refinement of texture. Thus there arise the calyces which we should be equally justified in regarding as corollas.

We have observed from the seed-leaves (cotyledons) upward a process of great expansion and development of the leaves to the periphery, while in the transition to the calyx we see once more a contraction from the circumferance towards the centre. We now notice that the corolla is produced by yet another expansion. The petals are usually larger than the calyx-leaves or sepals. Even as the organs were contracted into the calyx, so do they now expand again into petals under the influence of the still more finely filtered juices which have passed through the calyx to appear in a highly refined state as new and quite different organs. Their delicate organisation, their colour and their scent would make it quite impossible to recognise their origin if we were not able to hearken to Nature as she speaks to us through her many vagrancies and abnormalities.

Thus, for instance, inside the calyx of a carnation a second calyx is often found which on the one hand, inasmuch as part of it is quite green, reveals its tendency to become a one-leaved, incised calyx, while on the other hand it is tom and jagged and beginning at the tips and edges to expand and to become tinted like the real petals. Through this we clearly recognise the relationship between the corolla and the calyx.

The relation of the corolla to the stem-leaves reveals itself in different ways. On many plants the stem-leaves are produced more or less coloured long before they approach the flowering state; in other cases they become completely coloured when they get near to the flower.

Sometimes, too, Nature proceeds immediately to the corolla, omitting the calyx altogether and we are given the opportunity of observing the transformation of stem-leaves into petals. On tulip stalks, for example, an almost perfectly formed and coloured petal may sometimes be seen. Indeed it is even more remarkable when such a leaf, half green and half coloured, belongs with its green part to the stem and remains attached thereto, while its coloured part is carried up into the corolla so that the leaf is torn in two.

It is a not unlikely opinion which would ascribe the colour and scent of the petals to the presence of the male seed within them. It may be there in an insufficiently separated state, combined with and diluted by other juices. The mani-fold and beautiful appearances of colour incline us to the thought that the substance contained in the petals, although it is in an extremely purified condition, has not yet attained the very highest degree of purity, which would be white, absolutely without shade or colour.

CHAPTER VI
THE FORMATION OF THE STAMENS

The opinion set forth in the preceding paragraph appears still more probable when we think of the near relationship of the petals with the stamens. If the relationship between all the other organs were so obvious, so generally noticed and set beyond doubt, the present essay might seem superfluous.

Nature shows us this transition between petals and stamens taking place normally in several instances, in Canna, for example and in other plants of this family. Here a true but slightly changed petal contracts at the upper edge and an anther appears, in relation to which the rest of the petal takes the place of the filament.

In those plants which often produce double blossoms we can observe this transition in all its stages. In many kinds of roses, among the perfectly formed and coloured petals, other petals may appear which are contracted partly in the middle and partly at the sides. This contraction is caused by a little weal or protuberance which more or less resembles a perfect anther, while in just the same proportion the petal begins to take on the simpler form of a stamen. In some double poppies, fully developed anthers rest on petals of the thickly filled corolla which are very little changed; in others the petals are more or less drawn together by anther-like weals.

If all the stamens change into petals the flower will be seedless, but if in a flower which appears double, stamens are still developed, then fertilisation will take place.

Thus a stamen is produced when the organs, which until now we have seen expanding into petals, reappear in an extremely contracted and at the same time refined state. This once more confirms the truth of the observation put forward above, and we are made more and more aware of the alternating process of contraction and expansion whereby Nature at last reaches her goal.

CHAPTER VII
NECTARIES

Quick as the transition is in some plants from the corolla to the stamens, we perceive that Nature is not able to complete it in one step, but produces intermediate organs which resemble in form and effect sometimes one part of the plant and sometimes another. Although they vary greatly in form these organs may mostly be united under one heading: they are slow transitions from the petals to the stamens.

In effect, most of those variedly formed organs, which Linnaeus called nectaries, may be thus defined, and here again we have occasion to admire the keen power of penetration of this extraordinary man, who, without coming to a perfectly clear understanding of the function of these parts, trusted to his intuitive feeling and ventured to give a single name to such seemingly different organs.

Various petals show us their relationship to stamens; without noticeably changing their form they have little cavities or glands which secrete a kind of honey-juice. That this juice is a yet unelaborated and not yet fully differentiated fertilizing fluid we can to some extent surmise from the above considerations, and we shall be supported in this by further reasons which will be brought forward later on.

The so-called nectaries may also appear as independent organs and then they are formed sometimes like petals, sometimes like stamens. Thus, for example, the thirteen filaments, each with its little red ball, on the nectaries of Parnassia, very much resemble stamens. Others look like stamens without anthers, as for example in Valisneria or Feuillea, while in Pentapetes we find them in a circle alternating regularly with the stamens and in leaf-like form. In systematic descriptions too these organs are called Filamenta castrata petaliformia. Similar ambiguous forms are to be seen in Kigellaria and the Passion-flower.

In this sense the “secondary corollas” seem likewise to deserve the name of nectaries. For if the forming of the petals comes about through a kind of expansion, the secondary corollas on the other hand are formed by contraction, that is to say, in just the same way as the stamens. And so we see within perfectly expanded corollas smaller, contracted, secondary ones, as for example in the Narcissus, in Nerium and in Agrostemma.

Furthermore, in various species we see alterations which are still more striking and remarkable. In some flowers we notice a little hollow filled with honey-like juice at the inner base of the petals. This little cavity becomes deeper in some species and types than in others and produces on the back of the petal a spur or horn-like protuberance, the shape of the rest of the petal being at the same time more or less modified. This can be distinctly seen in many types and variations of Aquilegia.

Wefind the nectary most transformed in Aconitum and in Nigella, but even here only a little attention will enable us to see its resemblance to a leaf. In Nigella especially it tends to grow into a leaf or petal and through the transformation of the nectaries the flower becomes double. In Aconitum it is easy to see the resemblance of the nectaries to the domed-shaped petals under which they are hidden.

Having already said that the nectaries are a transitional stage between petals and stamens we may at this point say a few words about irregular flowers. The five outer petals of Melianthus, for example, could be described as true petals, but the five inner ones as a secondary’ corolla consisting of six nectaries, of which the uppermost nearly resembles the leaf-form while the lower—which is indeed called the nectary—differs most from it. In this same sense the carina or keel of the Papi-lionaceae might be called a nectary in so far as it, of all the petals of this flower, is nearest in form to the stamens and differs greatly from the leaf-like form of the so-called vexilli. In this way too we may easily explain the brush-like appendages which are attached to the end of the carina of some species of Polygala: so shall we form a distinct idea of the real meaning of these organs.

It is hardly necessary to avow that these remarks are not intended to bring into confusion all that has hitherto been separated and classified through the endeavours of observers and systematists. We only wish to explain more clearly the variable formations and developments of the plant-kingdom.

CHAPTER VIII
MORE ABOUT THE STAMENS

Microscopic observations have placed it beyond doubt that the generative organs of the plants as well as other organs are produced by spiral vessels. We take this as a basis for the argument that the different parts of the plant, which have so far manifested themselves to us in such varied forms, are none the less intrinsically the same.

Now as the spiral vessels are situated in the middle of the bundles (vascular bundles) and are enclosed by them, we can to some extent come to a better understanding of the above-mentioned strong contracting force if we imagine the spiral vessels, which really look like elastic springs, exerting their utmost power so that they overcome the expansive tendency of the sap-vessels.

The shortened vascular bundles can then no longer expand; they are not able to unite so as to form a network by anastomosis, and the cellular tissue, which otherwise fills up the spaces of the network, can no longer develop. Here, all the causes for the expansion of stem-leaves, calix and petals are at an end, and there appears a frail, extremely simple thread or filament.

Hardly are the fine little membranes of the anther formed, than the extremely delicate vessels terminate in them. Now if we admit that here the very same vessels, which otherwise become lengthened and expanded and united with one another, are at this stage in an extremely contracted condition; if, moreover, we see coming from them the highly developed pollen which through its active energy compensates for what the vessels that have brought it forth have lost in their power of expansion; if when set free it seeks the feminine parts which through the same working of Nature have grown up near the stamens; if it attaches itself fast to the pistils and imparts its influence to them—then at long last we are not disinclined to call the union of the male and female organs a spiritual anastomosis, and we believe we have brought the concepts of growth and reproduction, at least for a moment, a little nearer to one another.

The fine substance, which is developed in the anthers, looks like a kind of dust; but these little balls of pollen are in fact vessels or cells for the preservation of an extremely refined juice. We agree with the opinion of those who maintain that this juice is absorbed by the pistils to which the pollen-balls attach themselves, fructification being in this way effected. This becomes even more credible when we think that some plants do not give off pollen grains, but only a kind of fluid.

We are here reminded of the honey-like juice of the nectaries and its probable relation to the more elaborated fluid of the pollen grains. Perhaps the nectaries are organs for preparation and maybe their honey-like moisture is drawn in by the anthers and then more fully perfected and elaborated—quite a plausible opinion, for this sap is no longer to be seen after fructification.

We will not omit to mention here in passing that the filaments as well as the anthers, grow together in many different ways, showing what we have so often described, namely the anastomosis and union of organs which in their beginnings were quite apart and distinct.

CHAPTER IX
FORMATION OF THE STYLE AND STIGMA

If until now I have tried to show as far as has been possible that the different parts of the plant as they develop one after the other, even though they may greatly differ in outward form, are intrinsically the same, it will easily be surmised that my aim will now be to explain in this way too the structure of the feminine parts.

At first we will consider the style and stigma of the pistil apart from the actual ovary, as indeed, we often find it in Nature. This we may the more easily do, as it reveals a characteristic and distinct form.

We observe then, that the pistil is at the same stage of growth as the stamens. We noticed that the stamens were produced through a contraction; this is also often the case with the styles, and we see that, though not always just the same length as the stamens, yet they are only a little longer or shorter. In many cases the style looks almost like a filament without an anther, and the two are more nearly allied in exterior form than any of the remaining parts. As they are both produced by spiral cells, we see all the more clearly that the feminine part is no more a distinct organ than the masculine part, and when through this observation the close relationship of these feminine parts with the masculine becomes evident to us, we find it all the more appropriate and illuminating to think of their union as a kind of anastomosis.

We very often find the pistil formed by the growing together of several single ones, the component parts being hardly distinguishable at the tip, where they are not even separated. This growing together, the effect of which we have often remarked upon, takes place in this instance most easily of all. Indeed, it must happen, for the delicate organs, before they are perfectly developed, are pressed together in the blossom and thus enabled intimately to unite with one another.

In various normal cases Nature shows us more or less clearly the near relationship of the pistil with the preceding parts of the blossom. For example, the pistil of the iris appears with its stigma in the perfected form of a petal. The umbrella-shaped stigma of Sarracenia shows that it is composed of several leaves set together. True, this is not so marked and yet even the green colour is retained. With the help of the microscope we find more stigmas formed like perfect one- or many-leaved calyces in the crocus, for example, or Zannichellia.

By a retrogressive development Nature often shows us instances where the style and stigma have changed back again into petals; the Ranunculus asiaticus, for example, becomes double in this way, the stigmas and styles having transformed themselves into true petals, while the anthers, immediately underneath, may often be found unchanged. One or two other remarkable instances will come to our attention later on.

We will here repeat the observations already made: that pistil and the stamens are at the same stage of growth and illustrate once again the fundamental principle of alternate expansion and contraction. From the seed to the most perfect development of the stem-leaf we first observe expansion; then we saw the calyx being formed through a contraction; the petals by expansion; the reproductive organs again by contraction; and now we shall soon become aware of the greatest expansion and contraction of all, namely the expansion in the fruit and the contraction again in the seed. In these six steps Nature continually completes her endless work of the propagation of plants by the two sexes.

CHAPTER X
THE FRUITS

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.

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.

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.

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.

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.

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.

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.

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

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.

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

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

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.

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.

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.

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.

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. After separation the bud is nourished either by the new plant on which it has been grafted, or by means of the roots which it forms immediately when planted in the soil.

The eye consists of nodes and leaves in a more or less developed condition, destined to enlarge and expand the growing plant.

In effect, the side twigs which sprout from the nodes may be regarded as distinct little plants, growing on the parent plant just as the latter grows in the earth.

The comparison of seed and eye has so often been made, and especially quite recently, with such penetration and exactitude, that we can but appeal to this work with unqualified approbation.

We will only state the following: In highly organised plants nature makes a clear difference between eyes and seeds. In more simply formed plants, however, this difference no longer seems apparent, even to the most acute observer. There are seeds which are undoubtedly seeds, and eyes which are undoubtedly eyes, but it is only possible to conceive, and not in any outward way to see, where the line of demarcation lies between properly fertilised seeds, separated from the parent plant by the reproductive process, and propagative buds which simply push their way out from the parent plant and separate from it without any apparent cause.

Having weighed this well in our minds we may venture to think that seeds, though they differ from eyes by being completely enclosed, and from propagative buds by the visible cause of their formation and separation from the parent plant, are yet closely related to both.

CHAPTER XIV
FORMATION OF COMPOSITE FLOWERS AND FRUITS

We have so far tried to explain by the transformation of the stem-leaves, the formation of single flowers and also seeds produced within a closed capsule. Closer examination will show that in these instances no eyes are developed; indeed there is absolutely no possibility for such a development to take place. To understand the composite flower however, as well as the compound fruit gathered around a single cone, spindle, dies or the like, we must look to the development of eyes.

We often see that stems, without preparing long beforehand or reserving their energy for the development of a single flower, bring forth blossoms already at their nodes, often continuing in this way uninterruptedly to the very tip. This may be explained however by the theory already propounded. All flowers developed from eyes may be regarded as distinct plants growing on the parent plant, just as the parent plant grows on the earth. Supplied, however, as they are with purer juices by the nodes, even the first leaves of the little twigs are much more finely formed than the first leaves of the parent plant which came after the cotyledons; indeed, even the immediate formation of calyx and flower is often possible.

Even these blossoms that develop out of eyes, had they received more copious nourishment, would have become twigs and have undergone a destiny similar to that of the parent plant.

During the development of such flowers from node to node, we notice too that same transformation of the stem-leaves which we observed when the transition to the calyx took place slowly. The leaves contract more and more, until at last they almost disappear. They are then called bracts, and have more or less lost their leaf-like form. Just in the same proportion as the stem becomes thinner, so do the nodes move closer together, and everything that happened in the transition to the calyx happens now, except that no particular terminal flower appears at the tip, because Nature has already fulfilled her task at each successive eye.

Now when we have contemplated well such a stem adorned at each node with a blossom, we shall more easily understand a composite flower, especially if we remember what has already been said about the origin of the calyx.

Nature forms a composite calyx, (involucre) from a number of leaves by pressing them close to one another and arranging them around an axis. With this same strong impulse of growth she develops, so to speak, one infinite stem, producing all its eyes at the same time and as near together as possible in the form of a flower, each separate floret fructifying the seed-vessel already prepared below it. Nor are the nodal leaves always entirely lost in this tremendous contraction. In thistles for example (compare Dipsacus laciniatus), the little leaf faithfully accompanies the floret which grows from the eye situated close by it. In many grasses, too, each flower has such a leaflet, which in this case is called a glume.

So we are led to see that the seeds of a composite flower are true eyes, formed and developed by means of the male and female organs. We shall easily be convinced that this is so if, keeping this idea always in mind, we examine and compare the growth and manner of seeding of various plants.

Then, too, we shall not find it difficult to explain the seeds—whether enclosed within a seed-vessel or not—which are produced in the middle of a single flower. For it comes to the same thing if a single flower surrounds a compound ovary, whose united pistils suck in the fertilising juices from the anthers and pass them on to the ovules, or if each ovule has its own pistil, and anthers and petals.

We are convinced that with a little practice it would not be difficult to explain in this way the manifold forms of flowers and fruits. But it would of course require complete familiarity with the above stated ideas of expansion and contraction, approximation and anastomosis, to be able to apply them in their right place as one would use algebraic formulae. And as much depends on the exact observation and comparison of the various stages through which Nature passes, both in the forming of genera, species and varieties, and in the growth of each individual plant, a collection of illustrations made for this purpose with explanations of the different parts of the plant in botanical terminology would be both welcome and useful. Two strange instances of proliferous flowers, if we could have them before us, would help most decidedly in upholding this theory.

CHAPTER XV
A PROLIFEROUS ROSE

All that we have been seeking to grasp by powers of imagination and thought is shown most clearly in the instance of the proliferous rose. The calyx and corolla are arranged and developed around the axis; but instead of the seed-vessel contracted in the centre of the blossom, with the masculine and feminine organs arranged around, the stem, half red and half green, continues upward, while from it arise in succession smaller, dark red, folded petals, some of them bearing traces of anthers. The stem goes on growing, thorns appear on it again, the coloured petals which now appear singly become smaller and at last transform into variegated stem-leaves, half red and half green; a series of regular nodes is formed and from their eyes small, though imperfect, rosebuds appear once more.

This example in particular affords visible proof of our theory, namely, that all calyces are simply leaves, folia floralia, contracted and growing together at the periphery. For in this specimen the calyx, gathered round the axis, consists of five perfectly developed, compound leaves of three or five leaflets, such as are normally produced by rose branches at their nodes.

CHAPTER XVI
A PROLIFEROUS CARNATION

Strange as this phenomenon will appear to us when we contemplate it, yet another—a proliferous carnation—is still more remarkable. We see a perfect flower with a calyx and a double corolla; in the centre is a seed-capsule, not, however, quite fully developed. From the sides of the corolla four new and perfect flowers are developed, separated from the parent-flower by stalks three or four nodes or more in length. These new flowers, too, have calyces and double corollas, formed not so much of single petals as of little crowns of petals united at their base, or more often of petals which have developed like little twigs and grown together round a stem. Notwithstanding this monstrous development, filaments and anthers are present in some of these flowers. Fruit capsules are there with their styles, the capsules appearing again in leaf-form. Indeed, in one flower the seed-vessels were united into a perfect calyx and contained the rudiments of another complete, double flower.

While the rose was like a half completed flower, from the centre of which the stem again shot upward, bearing stem-leaves as before, the carnation, with a well formed calyx and perfect corolla and a capsule situated properly in the centre, had developed eyes from among the surrounding petals, producing actual twigs and flowers. We see, then, from these two instances, that Nature normally terminates the period of growth in the blossom—adds it up, so to speak, to a sum-total, so that by thus checking the possibility of gradual and infinite growth, she may achieve her aim the more quickly through the forming of seeds.

CHAPTER XVII
LINNAEUS’S THEORY OF ANTICIPATION

If here and there I may have stumbled on a path which one of my predecessors, though attempting it under the guidance of his great teacher, describes as so fearful and dangerous; or if I have not quite succeeded in levelling it and clearing it of every obstacle for those who come after me, yet I still hope that this will not have been a fruitless undertaking.

At this point it will be right to consider the theory by which Linnaeus sought to explain these phenomena. The things of which this essay treats could not have escaped his keen eye, and if we may now proceed from where he left off, we are indebted to the endeavours of so many observers and thinkers who have dispelled prejudices and cleared away many hindrances from our path. An exact comparison of his theory with one we have just propounded would take too long. Those acquainted with this subject will easily do this for themselves, and such a comparison would be too complicated to be easily intelligible to those who have never thought about these things. We will only point out briefly what hindered Linnaeus from making further progress and reaching the goal.

In the first place he made his observation on trees—complicated and long-lived plants. He saw that a tree planted in a fairly large pot and given too much nourishment produced branch after branch for several years, while the same tree, when restricted to a smaller pot, quickly produced flowers and fruit. He saw that the development which before was gradual, then took place all at once. He called this process of Nature “Prolepsis,”—an anticipation—because the plant in the six steps we have been observing, seemed to anticipate six years. He worked his theory out dealing chiefly with the buds of trees without paying particular attention to annual plants, perceiving no doubt that his theory did not fit them so well. For according to his teaching we would have to assume that each annual plant is really intended by Nature to grow for six years, but that in the flower and fruit it suddenly anticipates this space of time, and then fades.

We, on the contrary, first studied the growth of annual plants, and now it is easy to apply our deductions to plants of longer duration. For a bursting bud on the oldest tree may be thought of as an annual plant, even though produced from an old stem and capable itself of longer duration.

The second cause which held Linnaeus back was that he regarded the circles enclosed one within the other in the stem of the plant—the outer and inner bark, the wood, the pith—too much as being equally active, alive and essential, and to these different circles of the stem attributed the origin of the flower and fruit, because they too seem to encircle and develop from one another. This was, however, only a superficial idea which on closer examination can never be confirmed. The bark is, in fact, unfit for further reproduction and in long-lived trees becomes an obdurate mass on the outside and is separated from the wood within, which has also become quite hard. The bark of many trees falls away and in others it can be taken off without in the least damaging the tree, thus it could not possibly produce either a calyx or any other living part. It is the layer immediately within the bark which has all the power of life and growth, and to the extent that this is injured, the growth of the whole will be disturbed. We shall see too, on closer investigation, that this is the layer which produces all the external parts of the plant—one after the other in the stem, and simultaneously in the flower and fruit. Linnaeus only ascribed to it the subordinate work of producing the petals. To the wood on the other hand, he attributed the all important production of the stamens, although one can clearly see that it is a part which has solidified into a passive condition, durable perhaps, but dead to any stirring of life. And finally the pith was supposed to perform the most important task of all—the production of the feminine organs and subsequently a numerous posterity. The doubts which have been raised as to the great importance of the pith and the reasons for refuting this opinion seem to me weighty and conclusive. It only seemed as though pistil and fruit were developed out of the pith, because these forms, when first we see them, are in a soft undefined state resembling pith or parenchyma, and also because they are pressed together in the centre of the stem where we are accustomed to see the pith.

CHAPTER XVIII
SUMMARY

I hope that the present attempt to explain the metamorphosis of plants may contribute something to the solution of these problems and provide occasion for additional comments and opinions. The observations on which my essay is based have already appeared singly and they have also been collected and classified. It will soon be decided whether the step we have just taken is an approach toward the truth. As briefly as possible we shall summarize the chief results of the discussion up to this point.

When we consider a plant in relation to its vital force, we see this vitality manifesting itself in two ways : first, through vegetative growth, by development of stems and leaves; and next, through reproduction, which is completed in the formation of flower and fruit. If we examine the growth phase more closely, we see that the plant, as it vegetates and progresses from node to node, from leaf to leaf, is likewise carrying on a type of reproduction, which differs from that occurring in fruit and flower in that it is successive instead of sudden, appearing in a series of individual developments. Yet this vegetative force which exerts itself gradually is very closely related to the force which brings about a marked propagation in one step. Under certain circumstances a plant can be forced to vegetate continuously; and on the other hand, its flowering can be accelerated. The former situation occurs when there is a considerable influx of cruder saps, and the latter when more rarefied forces are preponderant.

By referring to vegetative growth as a successive reproduction, and to the formation of flowers and fruits as a simultaneous one, we have actually characterized the manner of their development also. A plant which vegetates, is expanding more or less: it develops a stalk or stem, the distances from node to node are usually considerable, and its leaves spread out from the stem on all sides. Conversely, a plant which flowers, is contracting all its parts : increments in length and breadth are arrested, and all its organs, developing in close propinquity, are in a highly concentrated state.

Whether then the plant vegetates, blossoms, or bears fruit, it nevertheless is always the same organs, with varying functions and with frequent changes in form, that fulfill the dictates of Nature. The same organ which expanded on the stem as a leaf and assumed a highly diverse form, will contract in the calyx, expand in the petal, contract in the reproductive organs, and expand for the last time as fruit.

This process of Nature is at the same time bound up with another, with the assembling of various organs around one central point in fixed numbers and proportions—greatly exceeded and variously modified, however, in some flowers and under certain conditions.

Similarly, anastomosis is in operation during the formation of flowers and fruit, closely uniting the compact and extremely delicate parts of the fructification, throughout their existence or for only part of it.

Yet these phenomena of approach, centralization, and anastomosis are not peculiar to flowers and fructifications alone; indeed we can observe something similar in the cotyledons, and other plant parts will furnish us with abundant material for similar reflections in the sequel.

We have ventured to trace back to the leaf form those fruits in which the seeds are firmly enclosed, just as we sought to show that the organs of the vegetating and flowering plant, though seemingly dissimilar, all originate from a single organ, namely, the leaf, which usually develops at each node.

It is self-evident that we ought to have a general term with which to designate this diversely metamorphosed organ and with which to compare all manifestations of its form. At present we must be content to train ourselves to bring these manifestations into relationship in opposing directions, backward and forward. For we might equally well say that a stamen is a contracted petal, as that a petal is a stamen in a state of expansion; or that a sepal is a contracted stem leaf approaching a certain stage of refinement, as that a stem leaf is a sepal expanded by the influx of cruder saps.

We may likewise say of the stem that it is an expanded flowering and fruiting phase, just as we have predicated of the latter that it is a contracted stem.

Moreover, I have at the close of the treatise considered also the development of eyes and have thereby attempted to explain compound flowers and unenclosed fruits as well.

In this way, then, I have endeavored to set forth, as clearly and completely as I could, a theory which to me has much that is convincing. However, if my theory has not been conclusively demonstrated, if it should still contain contradictions, or if the method of interpretation it employs should not seem at all times applicable : all the more shall I consider it my duty to take note of all criticism and to give the material more exact and extended treatment in the sequel, thereby making this approach to the subject more graphic, and winning for it more universal approbation than can perhaps be expected at present.