386 The Movements of Plants 



The whole of his physiological work may be looked at as an 

 illustration of the potency of his theory as an "instrument for the 

 extension of the realm of natural knowledge 1 ." 



His doctrine of natural selection gave, as is well known, an im- 

 pulse to the investigation of the use of organs and thus created the 

 great school of what is known in Germany as Biology a department 

 of science for which no English word exists except the rather vague 

 term Natural History. This was especially the case in floral biology, 

 and it is interesting to see with what hesitation he at first expressed 

 the value of his book on Orchids 2 , " It will perhaps serve to illustrate 

 how Natural History may be worked under the belief of the modifica- 

 tion of species" (1861). And in 1862 he speaks 3 more definitely of 

 the relation of his work to natural selection : " I can show the 

 meaning of some of the apparently meaningless ridges [and] horns ; 

 who will now venture to say that this or that structure is useless?" 

 It is the fashion now to minimise the value of this class of work, and 

 we even find it said by a modern writer that to inquire into the ends 

 subserved by organs is not a scientific problem. Those who take this 

 view surely forget that the structure of all living things is, as a whole, 

 adaptive, and that a knowledge of how the present forms come to be 

 what they are includes a knowledge of why they survived. They 

 forget that the summation of variations on which divergence depends 

 is under the rule of the environment considered as a selective force. 

 They forget that the scientific study of the interdependence of 

 organisms is only possible through a knowledge of the machinery of 

 the units. And that, therefore, the investigation of such widely 

 interesting subjects as extinction and distribution must include a 

 knowledge of function. It is only those who follow this line of work 

 who get to see the importance of minute points of structure and 

 understand as my father did even in 1842, as shown in his sketch of the 

 Origin*, that every grain of sand counts for something in the balance. 

 Much that is confidently stated about the uselessness of different 

 organs would never have been written if the naturalist spirit were 

 commoner nowadays. This spirit is strikingly shown in my father's 

 work on the movements of plants. The circumstance that botanists 

 had not, as a class, realised the interest of the subject accounts for the 

 fact that he was able to gather such a rich harvest of results from 

 such a familiar object as a twining plant. The subject had been 

 investigated by H. von Mohl, Palm, and Dutrochet, but they failed 

 not only to master the problem but (which here concerns us) to 

 give the absorbing interest of Darwin's book to what they discovered. 



1 Huxley in Darwin's Life and Letters, H. p. 204. 



2 Life and Letters, in. p. 254. s Loc. cit. 

 4 Now being prepared for publication. 



