246 The Physiology of Plants BOOKIII 



problems were regarded from the new standpoint, and by 

 slow degrees the conception of the chlorophyll apparatus 

 as a new factor, a mechanism concerned in the manufacture 

 of organic substance for nutrition of both animal and plant 

 made its way into scientific thought. The absorption of 

 gases from the air came to be recognized as a part of this 

 preliminary work and not necessarily confined to the vege- 

 table organism, though occurring only very exceptionally 

 in the animal world. The chlorophyll apparatus in fact 

 came to be looked on as something sui generis, not neces- 

 sarily more vegetable than animal, concerned only with 

 the manufacture of food for both, though located for the 

 most part only on one side of the ill-defined border between 

 them. This distribution, moreover, was associated with 

 the stationary as contrasted with the locomotory habit. 



While the whole face of this section of physiological study 

 was changed, the second factor alluded to brought about 

 an equally extensive alteration in another. Darwin's great 

 work, the influence of which on morphological speculation 

 we have already examined, was co-operating with the first 

 cause just discussed, and the phenomena of the reaction 

 between organism and environment came into review and 

 received further investigation. The new theory gave the 

 death-blow to all the merely mechanical explanations of 

 vital phenomena that had hitherto held the field and which 

 were little more than gropings in the dark. So the 

 physiology of the period we are considering assumed an 

 importance and obtained a development which would have 

 seemed incredible even to any of the most enthusiastic 

 workers of the time. Research brought in its train literature, 

 discovery succeeded discovery, and by the end of the 

 period the observers of the new century were able to realize 

 that the physiology of plants had ceased to be a subordinate 

 section of botany and had attained to the rank of an 

 independent science. 



