322 Proceedings Portland Society Natural History 



tion in mind, there would be but two climatic formations in 

 eastern North America: a coniferous forest extending 

 southward from the arctic to the St. Lawrence valley; and 

 a deciduous forest occupying the rest of the area. 



Such a view-point, although ecologically correct, would, 

 however, fail to recognize the existence of the Transition 

 region, which, as already pointed out, is very distinct in 

 both the nature of its climax forest and floristically as well. 



It must be constantly borne in mind that we are con- 

 cerned merely with the more conspicuous and extensive fea- 

 tures of the vegetation as displayed by the various climax 

 associations. Consequently it will be impossible to consider 

 the minor local variations which often obscure the true con- 

 ditions. It must be admitted that differences in topography 

 and soil profoundly affect the vegetation and may even 

 bring about physiographic climaces. However, these local 

 variations in the physiographic factors, unless they are op- 

 erative over extensive areas, are of prime importance only 

 from the standpoint of floristic plant geography — the study 

 of the distribution of individual species ; and they are negli- 

 gible in a survey of the distribution of masses of plants. 

 These two viewpoints are both of value in the study of plant 

 geography and they are not antagonistic, but simply ap- 

 proach the subject from different angles. The floristic 

 plant geographer is interested primarily in the unusual oc- 

 currence of individual species, while his ecological co-worker 

 is concerned with the usual and more general features of the 

 vegetation as a whole. 



To sum up, in the opinion of the writer, the following 

 forest regions should be distinguished in eastern North 

 America. 



A. The Northeastern Evergreen Coniferous Forest Re- 

 gion. This area extends southward from the arctic tundra 

 to the Great Lakes and the height of land, which borders the 

 St. Lawrence valley on the north. For our purposes its 

 southern limit may be assumed to coincide with the north- 



