312 George E. Nichols, 



uplands may likewise be well represented. Of special interest, 

 however, is the conspicuous position commonly occupied by the 

 mosses and liverworts, which, in favorable situations, may 

 develop luxuriantly, growing either in crevices or on sloping or 

 perpendicular rock surfaces. Representative species are listed 

 below, and, in addition to these, various of the species of wet 

 cliffs (p. 370) may grow here. 



Bazzania tricrenata Tortella tortitosa 



Diplophylliim taxifoliuni Racomitriuni fasciculare 



Porella platyphylloidea Ulota americana 



Radula complanata Pohlia cruda 



Lejeunea cavifolia Bartramia pomiformis 



Andreaea petrophila Hedivigia albicans 



Sivartsia montana Drepanocladus aduncus 



Fissidens osmundoidcs Polytrichiim olpimim 



The ravine forest. — Nowhere in the lowland of northern Cape 

 Breton are forests of the coniferous type more luxuriantly 

 developed than in ravines. In general, these forests conform 

 closely with the regional climax type of the mountains, and 

 need not be described in detail at this point. Such forests here 

 represent an edaphic climax association-type, and as such their 

 development is correlated very largely with local peculiarities of 

 temperature and soil moisture. They are best developed on 

 north-facing slopes, where the failure of the succession to pro- 

 ceed beyond the coniferous forest stage may be attributed to the 

 slowness with which the snow melts and the ground thaws out in 

 spring and to the relatively low temperatures which obtain 

 throughout the season. Quite commonly the north-facing slope 

 of a ravine supports a coniferous forest while the opposite, south- 

 facing slope is clad with a forest of the regional climax type. 

 On north-facing slopes, coniferous climax forests are by no 

 means confined to ravines : one of the most distinctly boreal 

 examples of upland forest which has come to the writer's atten- 

 tion in the lowland is situated along the lower slopes of a steep 

 mountain side, where ice frequently lingers as late as August, 

 notwithstanding the fact that it faces an open intervale which 

 was formerly occupied by a deciduous forest. In ravines which 



