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it has become a classic in scientific literature was originally only intended as a preliminary précis of a vast accumulation of facts and arguments which the author had collected. It was intended to be but the precursor of a series of works in which all the evidence was to be methodically set out and discussed. Of this vast undertaking only one portion, the Variation of Plants and Animals under Domestication, was ever actually published. Apart from its primary purpose it produced a profound impression, especially on botanists. This was partly due to the undeniable force of the argument from analogy stated in a sentence in the introduction : “Man may be said to have been trying an experiment on a gigantic scale ; and it is an experiment which nature, during the long lapse of time, has incessantly tried.” But it was still more due to the unexpected use of the vast body of apparently trivial facts and observations which Mr. Darwin with astonishing industry had disinterred from weekly journals and ephemeral publications of all sorts and unexpectedly forced into his service. Like Molière's Monsieur Jourdain, who was delighted to find that he had been unwittingly talking prose all his life, horticulturists who had unconsciously moulded plants almost at their will at the impulse of taste or profit were at once amazed and charmed to find that they had been doing scientific work and helping to establish a great theory. The criticism of practical men, at once most tenacious and difficult to meet, was disarmed; these found themselves hoist with their own petard. Nor was this all. The exclusive province of science was in biological phenomena for ever broken down; every one whose avocations in life had to do with the rearing or use of living things, found himself a party to the "experiment on a gigantic scale,” which had been going on ever since the human race withdrew for their own ends plants or animals from the feral and brought them into the domesticated state.

Mr. Darwin with characteristic modesty had probably underrated the effect which the Origin of Species would have as an argumentative statement of his views. When he came to realise this, it probably seemed to him unnecessary to submit to the labour of methodising the vast accumulations which he had doubtless made for the second and third instalments of the detailed exposition of the evidence which he had promised. As was hinted at the commencement, his attention was rather drawn away from the study of evidence already at the disposal of those who cared to digest and weigh it, to the exploration of the field of nature with the new and penetrating instrument of research which he had himself forged. Something too must be credited to the intense delight which he felt in investigating the phenomena of living things. But he doubtless saw that the work to be done was to show how morphological and physiological complexity found its explanation from the principle of natural selection. This is the idea which is ever dominant. Thus he concludes his work on climbing plants: “It has often been vaguely asserted that plants are distinguished from animals by not having the powers of movement. It should rather be said that plants acquire and display this power only when it is of some advantage to them ; this being of comparatively rare occurrence, as they are affixed to the ground, and food is brought to them by the air and rain.” The diversity of the power of movement in plants naturally engaged his attention, and the last but one of his works

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in some respects perhaps the most remarkable of his botanical writings—was devoted to showing that this diversity could be regarded as derived from a single fundamental property : “ All the parts or organs of every plant while they continue to grow . . . are continually circumnutating.” Whether this masterly conception of the unity of what has hitherto seemed a chaos of unrelated phenomena will be sustained time alone will show. But no one can doubt the importance of what Mr. Darwin has done in showing that for the future the phenomena of plant movement can and indeed must be studied from a single point of view.

Along another line of work Mr. Darwin occupied himself with showing what aid could be given by the principle of natural selection in explaining the extraordinary structural variety exhibited by plant morphology. The fact that cross-fertilisation was an advantage, was the key with which, as indicated in the pages of the Origin of Species, the bizarre complexities of orchid flowers could be unlocked. The detailed facts were set out in a well-known work, and the principle is now generally accepted with regard to flowers generally. The work on


insectivorous plants gave the results of an exploration similar in its object, and bringing under one common physiological point of view a variety of the most diverse and most remarkable modifications

of leaf-form.


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In the beginning of these remarks the attempt has already been made to do justice to the mark Mr. Darwin has left on the modern study of geographical botany (and that implies a corresponding influence on phyto-palæontology). To measure the influence which he has had any other branches of botany, it is sufficient to quote again from the Origin of Species: “The structure of each part of each species, for whatever purpose used, will be the sum of the many inherited changes through which that species has passed during its successive adaptations to changed habits and conditions of life." These words may almost be said to be the key-note of Sachs's well-known text-book, which is the most authoritative modern exposition of the facts and principles of plant-structure and function; and there is probably not a botanical class-room or workroom in the civilised world where they are not the animating principle of both instruction and research.

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