320 Proceedings Portland Society Natural History 



erous forest by most phytogeographers. Nichols, however, 

 has shown that in Cape Breton (23) the mixed deciduous 

 evergreen forest is the regional climax and is attained on 

 all physiographically favorable sites. The same condition 

 obtains in northern Maine and adjacent New Brunswick 

 (11) where similar forests occupy the better soils. On the 

 poorer sites — the sterile slopes, swamps or poorly drained 

 fl a t s — a coniferous forest is dominant, but it constitutes a 

 physiographic rather than a regional climax. 



It might be argued that, since so much of the forest in 

 such a region is coniferous, the climate must be such that a 

 coniferous growth is favored and consequently the region 

 should be considered as actually a part of the northeastern 

 coniferous climax. The climate may be favorable for the 

 balsam fir and spruces, but it is equally favorable for the 

 deciduous climax trees, and these latter always win out in 

 competition with the coniferous ones wherever edaphic and 

 topographic factors are favorable, due, in part, to the in- 

 ability of the conifers to successfully compete witli the de- 

 ciduous forms, owing to the nature of the trees themselves. 

 In view of these facts it seems best to consider this portion 

 of the Transition region as a northward extension of the 

 deciduous forest formation, although, as in the preceding 

 zone, there is a difference in the component species of the 

 climax forest. The coniferous forest in this zone, as al- 

 ready stated represents merely a physiographic climax. 



A study of the northward migration of plant life after 

 the Glacial Period also leads us to classify the Transition 

 region as deciduous rather than coniferous. We know from 

 geological evidence that in all probability the climate di- 

 rectly preceding the Ice Age was much warmer than at pres- 

 ent, with the result that southern broad-leaf species were 

 able to exist as far north as Greenland, and this sort of veg- 

 etation was much more widespread. The advent of the ice 

 sheet drove all existing life before it toward the south and 

 this movement was halted only when the advance of the 



