24 ECOLOGY AND ITS IMPORTANCE [CHAP. 



classification such being the professed and 

 useful work of the older botanists as Bentham 

 and the Hookers and the present systematists 

 at Kew. The ecologist asks of nature what 

 is the meaning or use of every point in the 

 details of structure observed, morphological and 

 anatomical ; and he finds, by noting as well, 

 every detail of the surrounding conditions of 

 the plant under investigation that the first result 

 of direct ecological observation, is that their 

 structure is in adaptation to the environment. 



He then groups plants into " associations " 

 according to their environments, and calls plants 

 of dry districts xerophytes ; of moist, marshy 

 places, hygrophytes ; true aquatic plants bring 

 hydrophytes, and all of an intermediate character, 

 mesophytes. Of course, every degree of transi- 

 tion between such typical groups occurs, and 

 special sub-types can be recognised. Thus, high 

 Alpine and Arctic plants are sub - types of 

 xerophytes, as well as succulent, maritime 

 plants, etc. 



The second step is to find out how the plants 

 acquired their adaptive structures. He first 

 proceeds inductively, by noticing that similar 

 structures are found in plants of no affinities 

 in widely separated countries, but possessing 

 similar conditions of soil and climate. Hence 

 arise "representative" or "mimetic" forms, as 

 those alluded to, the Cactacece of Mexico, and 



