CLASSIFICATION OF PLANT COMMUNITIES 351 



B. Secondary formations of the xerarch successional series 



a. Association-complexes due to cultivation 



b. Association-complexes due to fire 



0. Association-complexes due to logging 



C. Primary formations of the hydrarch successional series 



1. The formation-types of inland lakes and swamps 



a. The association-complexes of permanent lakes and ponds 



b. The association-complexes of periodic ponds 



c. The association-complexes of well-drained swamps 



d. The association-complexes of undrained swamps 



e. The association-complexes of poorly drained swamps 



2. The formation-types of lakes and swamps along the seadoast 



a. The association-complexes of salt and brackish marshes 



b. The association-complexes of brackish ponds 



D. Secondary formations of the hydrarch successional series 



The northeastern evergreen coniferous forest climatic formation 



1.. The regional climax association-type 

 II. The edaphic formation-complex .... etc. 



Explanatory remarks. In attempting to make an ecological 

 analysis of the climatic formation of a given region it seems logi- 

 cal that the subject matter be first arranged under two heads: 

 (I) The regional chmax association-type, and (II) The edaphic 

 formation-complex of the region. This division has aheady 

 been employed by Cooper (5), although he did not distinguish 

 the edaphic formations as such. An understanding of the region- 

 al chmax association-type, representing as it does the highest 

 degree of mesoph}i:ism permitted by the climate, is prerequisite 

 to the adequate interpretation of subordinate association-tj^^es 

 and of successional relations. The term edaphic formation, given 

 its developmental concept, of course includes the successions. 



The various edaphic formations which comprise the regional 

 edaphic formation-complex are next assembled into two suc- 

 cessional series which, adopting the terminology suggested by 

 Cooper (5, p. 11), are termed respectively the xerarch and the 

 hydrarch series. The term xerarch, to quote Cooper "is ap- 

 phed to those successions which, ha\4ng their origin in xero- 

 phytic habitats, such as rock shores, beaches, and cliffs, become 

 more and more mesoph>i;ic in their successive stages; [the term 

 hydrarch] to those which, originating in hydrophytic habitats, 



