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.

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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.

110

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.

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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

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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.

113

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.

114

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.

115

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.

116

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.

117

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.

118

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.

119

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.

120

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.

121

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.

122

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.

123

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.