GOOD: PLANT GEOGRAPHY 749 



opinion of the Geographie Botanique Raisonnee and his appreciation of its 

 author's generous attitude toward his own theories. 



Asa Gray's relation to the story of the Origin is different. He was one of the 

 few confidants whom Darwin had kept informed of the gradual development of 

 his own theoretical opinions about evolution. Indeed, one of his frequent letters 

 to Gray, which happened to express some of his ideas particularly concisely and 

 conveniently (as well as to date them), was included as part of the joint com- 

 munication of Darwin and Wallace to the Linnean Society of London by which 

 the theory of natural selection was launched on July 1, 1858. The exact rela- 

 tion of Gray's classic paper on the North American and Japanese floras to the 

 Origin is not simple to gauge now. This relationship was the subject of corre- 

 spondence between the two authors during the preparation of Darwin's great 

 work for the press, and it seems fair to regard Gray's paper as having been 

 written in a form intended to provide possible additional evidence for Darwin's 

 views. On the other hand Gray's formal attitude toward these views of Darwin's 

 was one of studied caution. Although Darwin considered Gray one of his most 

 valuable supporters, this support was tempered by a certain criticism because, 

 it would seem. Gray felt that a judicial attitude of this kind would be more effec- 

 tive aid in the long run than any more spectacular and enthusiastic championing. 



Hooker's two great papers were rather more profound phytogeographical 

 studies but are perhaps to be thought of as less intimately involved with the 

 trend toward evolution. They were obviously of great importance to it, since the 

 facts that they set forth spoke for themselvess in no uncertain voice. Of course 

 Hooker was even more closely associated with Darwin than was Gray but, to use 

 an apposite simile, the work of the two seems to illustrate convergence rather 

 than strict homology. It is perhaps an interesting commentary on this point that 

 Hooker, at any rate from 1850 to 1856, repeatedly expressed pessimistic opinions 

 about the progress and future of botany as a science, which suggests that he was 

 not altogether fully conscious of how rapidly the renaissance was approaching. 

 Let us hope that some of the pessimisms of today are equally ill-founded. 



However, we must not allow ourselves to wander farther down the by-ways 

 of evolutionary history, fascinating though these are. What has been outlined 

 has been intended to illustrate how opportune the founding of the Academy 

 was and to call attention to the three great botanists, de Candolle, Gray, and 

 Hooker, who dominated the phytogeographical scene at that time. There is never- 

 theless one other point about this birthday which must not be overlooked here, 

 namely, that it occurred only three years after California had become a state of 

 the Union. This surely is but further evidence, if such were needed, of that 

 intellectual leaven to which reference has already been made. 



With the coming of evolution the whole meaning of plant geography altered. 

 It has often been said that the real evidence of the truth of the theory of evolution 

 lies, not in this or that array of facts, but in its power as an organizing concept. 

 Without it, the facts appear chaotic; with it, they fall into order to a remarkable 

 degree. Nowhere is this more true than in plant geography, which is so funda- 

 mentally a mass of descriptive fact, and this is one of the reasons why it became 

 to tlie evolutionists one of the most promising and popular aspects of botany. 

 The other and even more important reason was the recognition, under the new 

 conception, of the inevitable relation between time, space, and change. All this 



