Vegetation of Northern Cape Breton. 259 



trees, the nature of the cHniax forest, taken in its entirety, is 

 intermediate between that of the evergreen coniferous, and that 

 of the deciduous chmatic formation, as most typically developed : 

 where, in other words, the two formations are telescoped. This 

 region represents a great tension zone, in which competition 

 between the northern and southern climax trees is still in active 

 progress, and where, as a result, it is possible to study the 

 ecological relations of the two groups of species concerned. The 

 northern boundary of this transition region is determined by the 

 northern outposts of the deciduous climax trees of the deciduous 

 forest formation : it may be regarded as coinciding approximately 

 with the northern limit of the sugar maple (see, in this connec- 

 tion. Cooper '13, pp. 36-39). In the same way, the southern 

 boundary of the transition region may be said to be determined 

 by the southern outposts of the climax trees of the evergreen 

 coniferous forest formation, in so far as these grow on uplands: 

 it may be regarded as coinciding roughly with the southern limit 

 of the balsam fir. These boundaries are indicated on the map 

 (Fig. i), but the lines as drawn can represent little more than a 

 rough approximation ; for, owing largely to variations in topog- 

 raphy, at higher elevations the evergreen coniferous forest 

 formation locally extends far to the south of the northern 

 boundary, while at lower elevations the deciduous forest forma- 

 tion is typically developed considerable distances north of the 

 southern boundary of the transition region, as here represented. 



From the standpoint of floristic plant geography it is signifi- 

 cant that the geographic center of distribution for the so-called 

 Canadian element in the flora of eastern North America lies 

 within this transition region. Many Canadian species are practi- 

 cally confined to this area, prominent examples of this latter 

 group, among the woody plants, being Piniis Strohns and P. 

 resinosa, Tsiiga canadensis, Betiila lutea, Acer pennsylvaniciim, 

 and Viburnum alnifolium. But while, from the floristic point of 

 view, the vegetation of this region certainly is more or less unique. 

 from an ecological point of view it is doubtfully to be regarded 

 as a distinct climatic formation. And while its intermediate 

 character is generally recognized, nevertheless, largely because of 

 the almost universal supremacy, in situations edaphically favora- 

 ble to their development, of the climax trees of the deciduous 

 forest formation over those of the northeastern evergreen conifer- 



