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’.” 
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’, “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* 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?” 
Tt 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 swmmation 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, m. p. 204. 
2 Life and Letters, u1. p. 254, 3 Loe. cit. 
“ Now being prepared for publication. 
