460 George E. Nichols, 



Thirty-five herbaceous vascular plants are listed as characteristic. 

 Bryophytes are present in profusion, but on the forest floor they 

 are sparsely developed. This latter fact apparently is correlated 

 with the annual accumulation on the ground of a blanket of 

 fallen leaves which prevents the development of a moss-carpet. 



The permanency of this type of forest is indicated by the com- 

 position of the younger generation of trees, which, in general, 

 conforms with that of the mature stand. In this connection the 

 ecological status in these forests of the balsam fir, character tree 

 of the northeastern evergreen coniferous forest climatic forma- 

 tion, is considered in some detail. The conclusion is reached 

 that the inability of this tree to compete successfully with the 

 trees which characterize the deciduous climax forest formation 

 can be attributed very largely to its shorter tenure of. life, 

 coupled with its greater susceptibility to fungus diseases and 

 possibly with its less pronounced tolerance of shade. 



The trees which characterize forests of the regional climax 

 type, not only here but elsewhere in the Transition Region, can 

 be divided into five groups: (A) Deciduous species whose center 

 of distribution lies south of the transition region; (B) 

 Deciduous species whose center of distribution lies within the 

 transition region; (C) Evergreen species whose center of dis- 

 tribution lies within the transition region; (D) Evergreen species 

 whose center of distribution lies north of the transition region; 

 (£) Deciduous species whose center of distribution lies north 

 of the transition region. With reference to the presence or 

 absence of representatives of the first four groups above specified, 

 eleven floristically different types of forest are distinguishable 

 (see p. 292). In general, the trees of groups B and C are 

 about equally well represented in forests throughout the 

 transition region, those of group A are most generally repre- 

 sented southward, those of group D northward. In many parts 

 of the transition region black spruce replaces balsam fir as the 

 predominant northern conifer. Black spruce does not appear to 

 be specifically distinct from red spruce. It is very doubtful 

 whether the various floristic subdivisions of the transition region 

 that have been defined should be regarded as ecologically distinct. 

 From the standpoint of ecological plant geography the vegetation 

 of the transition region as a whole is best treated merely as a 

 northward extension of the deciduous forest climatic formation. 



