2i6 THE BIOLOGY OF FLOWERING PLANTS 



supply, than are the mesophytic plants of meadows and 

 damp ravines. He examined a considerable number of 

 plants, and the general result is quite clear. It is, of course, 

 difficult to adapt exact methods to work in natural stations. 

 But the investigation points to an avenue of great possi- 

 bilities, and discloses an interesting way in which these two 

 great functions of the land plant co-operate in determining 

 the suitability of a plant to its habitat. 



