Vegetation of Northern Cape Breton. 277 



by cultivation, lumbering, or fire. The formations of the 

 xerarch and hydrarch series respectively are further subdivided 

 with reference to the general topographic features of the region, 

 these being considered from the standpoint of their relationship 

 to one another through physiographic development. Thus, 

 among the formations of the xerarch series, three groups of 

 formation-types are distinguished : the formation-types, respec- 

 tively, of ordinary uplands, of uplands along streams, and of 

 uplands along the seacoast. In the same way, the formation- 

 types of the hydrarch series fall more or less naturally into three 

 groups : the formation-types of lakes, ponds and swamps inland, 

 the formation-types in and along rivers and streams, and the 

 formation-types along the seacoast. The classification of forma- 

 tion-types primarily on the basis of water supply is open to cer- 

 tain objections, but so also is their classification primarily on the 

 basis of physiography, a method which might perhaps equally 

 well have been followed. 



In discussing the vegetation of each region, the regional 

 climax association-type is taken up first, since an understanding 

 of this, representing as it does the highest degree of mesophytism 

 permitted by the climate— the climatic indicator, so to speak, is 

 prerequisite to an adequate interpretation of subordinate asso- 

 ciation-types and of successional relations. The edaphic forma- 

 tion-complex of the region, which of course includes all the 

 edaphic formations and formation-types, with the associations 

 and association-types which comprise them, including the 

 regional climax association-type, is then considered, after the 

 manner outlined in the preceding paragraph. 



In matters of nomenclature the author, in general, has fol- 

 lowed the seventh edition of Gray's Manual ('08), with the 

 emendations of Robinson and Fernald ('09), for the vascular 

 plants, his own papers on the bryophytes of Cape Breton ('16^, 

 '18) for the mosses and liverworts, and Fink's Lichens of 

 Minnesota ('10) for the lichens. In the case of the vascular 

 plants, changes in nomenclature since the publication of the 

 Manual for the most part have been neglected. Only in excep- 

 tional cases are authorities cited for the names used. In 

 cases where a plant is referred to by its common name, the 

 scientific name is usually given only in connection with its first 

 mention in the text. 



