54 BOTANY 



a host of such facts to notice, but also the relation of 

 the various kinds of plants to each other. For instance, 

 many of our typical spring woodland flowers only grow 

 in the woodland community because at the time when 

 they are most in need of light the tall trees above them 

 have not yet got their leaves, and the light comes 

 sufficiently between the bare branches. In the eternal 

 shade of a wood composed of evergreens we do not 

 find the same carpet of flowers as in the light, deciduous 

 forests. 



One other illustration of this must suffice the Creep- 

 ing Willow and many other plants of the sand-dune 

 would never have been able to grow on the shifting 

 sand at all if it had not been for the sand-binding grass, 

 the Psamma, which forges ahead into the bare places, 

 and makes a substratum firm enough for the other plants 

 to inhabit. 



It will be realised, consequently, that the various 

 species are not only adapted to different features in the 

 environment, but that the peculiarities of one species often 

 prove to be most useful to another by preparing and 

 changing the physical features of available soil. The 

 morphologist and the anatomist look on the peculi- 

 arities of the individual as adaptations for its own 

 purposes, but the ecologist takes a broader view than 

 that and sees the various types interacting and inter- 

 dependent. 



Further even than this the ecologist must go and 

 see the plants actually affecting the physiography and 

 even the geography of some districts. A good illustra- 

 tion of this is seen in that very sand-grass just mentioned. 

 The loose sand thrown up by the sea is blown by the 

 wind to and fro and piled up in mounds only to be 

 scattered again as the wind changes, but once the creep- 



