INTRODUCTION 



The new currents of thought that set in from the time 

 of the appearance of the Origin of Species, and which, as 

 we have seen, were instigated by it, spread more widely 

 than seemed at first at all probable. The view that adapta- 

 tion to environment played so important a role in the 

 determination of external form commanded almost imme- 

 diate acceptance, and it needed only a little careful thought 

 to extend the idea to the details of internal structure. 

 Consequently the problems of anatomy began to be studied 

 in a new light, and new series of researches were under- 

 taken from i860 onwards, which were designed not only 

 to ascertain details of structure, but to determine also the 

 relation which these bear to function, and to ascertain how 

 far the action or the influence of the environment becomes 

 apparent in the construction of the tissues which serve to 

 constitute the organ. The members of the plant were 

 becoming rapidly to be recognized as organs, and the 

 importance of studying them from both points of view 

 found a ready acceptance among the anatomists of the 

 time. 



Moreover, the work of Hofmeister had prepared the way 

 for investigations on a scale different from any that had 

 prevailed, for he showed that there exists an essential 

 unity of type throughout the vegetable kingdom and opened 

 the way to a comparative study of the anatomy of the 

 vegetative parts which should supplement his own researches 

 on the reproductive structures. 



Another epoch-making research dates from about the 

 same time. The identification of the protoplasm of the 

 vegetable cell had been made by a few observers, especially 



