THE INTEGRATION OF THE ORGANIC WORLD. 399 



sense to integrate the two kingdoms ; needs not to be insisted 

 upon. Further complications of the mutual dependence will 

 be mentioned by and by. For the present it suffices to 

 recognize this division of organic functions as the first which 

 arose and as continuing to be that fundamental one which 

 more than all others binds organisms at large together. 



§ 314c. It will be thought by many readers that in speak- 

 ing of the contrasted vital activities of plants and animals as 

 constituting a "division of organic functions/' I am straining 

 words beyond their meanings ; since the conception of organic 

 functions postulates an organized whole in which they exist, 

 and plants and animals constitute no such organized whole. 

 But there is at hand an unexpected defence for this concep- 

 tion — a defence not forthcoming a generation ago, but which 

 now all biologists will recognize as relevant. I refer to the 

 phenomena of symbiosis. These present various cases in 

 which the plant-function and the animal-function are carried 

 on in the same body, — cases in which the cooperation is not 

 between separate vegetal organisms which accumulate nutri- 

 tive matters and separate animal organisms which consume 

 them, but is a cooperation between vegetal elements and. 

 animal elements forming parts of the same organism. 



As introductory to examples of these must first, however, 

 be named an example of such cooperation between the two 

 great classes of vegetal organisms — the fungoid and the al- 

 goid. Incredible as the statement once seemed, it is a state- 

 ment now accepted, that what we know as lichens, and used to 

 consider as plants forming a certain low class, are now found 

 to be not plants in the ordinary sense at all, but compound 

 growths formed Of minute algge and minute fungi, carrying 

 on their lives together: the algoa furnishing to the fungi 

 certain constituents they need but cannot directly obtain, 

 and the fungi profiting by certain materials they obtain from 

 the algae, either while living or while individually decaying. 

 Whence it would seem that after the microscopic vegetal 



