THE UNITS OF VEGETATION. 123 



Hence there is here no intention of setting up another antagonistic concept 

 of the formation, i. e., one based upon development. The actual recognition 

 of formations by means of physiognomy, of floristic, and of habitat has been 

 tried repeatedly by means of detailed and exact methods of quadrat and 

 instruments. This has afforded conclusive proof that no one of the three 

 viewpoints is adequate alone or primarily. This conclusion is reinforced by 

 the conflicting opinions of the advocates of the different concepts, but espe- 

 cially by the intensive study of the interrelations of community and habitat. 

 Every community not only owes its grouping or composition to the habitat, 

 but the species, and especially the dominant ones, take their characteristic 

 impress from it. While their reproduction-form or taxonomic form shows 

 this least for obvious reasons, the vegetation-form, growth-form, or life-form 

 usually affords a striking illustration of this fact, and the habitat-form is an 

 exact and universal record of it. On the other hand, the commimity modifies 

 the habitat materially or essentially by its reactions upon it, and the habitat 

 thus changed has a new action in selecting and modifying the species which 

 enter it. This maze of action and reaction continues from the beginning to 

 the end of the life-history of the formation, and it is as one-sided and unfortu- 

 nate to emphasize one process as it is the other. The habitat is the basic 

 cause, and the community, with its species or floristic, and its phyads and 

 ecads, or physiognomy, the effect. But the effect in its turn modifies the 

 cause, which then produces new effects, and so on until the climax formation 

 is reached. A study of the whole process is indispensable to a complete under- 

 standing of formations. One must perforce conclude that the results obtained 

 from the over-emphasis of physiognomy, floristic, or habitat are as incomplete 

 as the concept itself. The simultaneous study of aU the processes and facts 

 can not yield too much truth, and it is a distinct handicap to assume that a 

 single vicTvpoint can afford all or most of the truth. 



Significance of development. — It is for these reasons that development is 

 taken as the basis for the analysis of vegetation. It is not a single process, 

 but a composite of all the relations of community and habitat. It not only 

 includes physiognomy, floristic, and habitat, but it also and necessarily includes 

 them in just the degree to which they play a part, whatever that may be. 

 Development furnishes, not a new point of view more or less incomplete and 

 antagonistic to those already existing, but one which includes all the others 

 and harmonizes and definitizes them. Its importance is just as great and its 

 use just as fimdamental as in taxonomy. The artificial system of Linnaeus 

 was not mmatural because it failed to use natural characters, but because it 

 used only part of them, and these not in their most fundamental relations. 

 So, likewise, all the concepts of the formation and the methods of recognition 

 so far employed are natural in so far as they use a natural process or response, 

 and artificial in so far as they fail to correlate this with all the other equally 

 natural and important processes. Taxonomic systems have become natural 

 and hence fundamental in just the proportion that it has been possible to 

 ground them upon development. Development is likewise the only basis for 

 a natural system of formations. It is as indispensable to their recognition as 

 to their classification. 



Earlier suggestions of the developmental view.— The fact that development 

 has more than once been used in classifying communities indicates that the idea 



