118 PLANT LIFE 



the same, but the real causes responsible for 

 its appearance are equally obscure. The most 

 we can at present say is that in the exercise 

 of the function new conditions are introduced 

 which lead to the supply of abundant nutritive 

 material, together with the power to use it. 

 But the mode of interaction of all the inner 

 functional conditions is far too complex for 

 us to express the matter in any rough-and- 

 ready formula. Least of all is it useful to say, 

 in anthropomorphic fashion, that structural 

 peculiarities like those of climbers are due to 

 the plant having adapted itself to its environ- 

 ment. We readily discern that the plant is 

 adapted, but we know remarkably little about 

 the processes whereby this interrelation has 

 been brought about. It conduces neither to 

 clearness of judgment nor to the advance 

 of science to mistake more or less fanciful 

 descriptions for real explanations of complex 

 phenomena. 



Groups of plants such as climbers are 

 interesting for the very reason that they serve 

 to illustrate the fact that any species, what- 

 ever its ancestral origin, may join a specialised 

 biological class provided it has the capacity 

 for developing an appropriate structure. 

 Another biological group is constituted by 

 the higher water plants. These have, for the 

 most part, descended from terrestrial fore- 

 bears, and they display many significant 

 features of interest in connection with their 

 more recent environmental conditions. Some 



