Vegetation of NortJiern Cape Breton. 445 



here. The following additional species might be mentioned as 

 characteristic of wet bogs, although they may also occur to 

 some extent in bog meadows : Eriophorum callitrix, E. angusti- 

 folium, Carex pauciflora, C. paiipcrcida, Smilacina trifolia. 

 Beside these, various of the species of dry bogs, not yet men- 

 tioned, may be sparingly represented. But the vascular plants 

 are of subordinate importance to the sphagnums, and the funda- 

 mental dissimilarity between the vegetation of wet bog and that 

 of bog" meadow lies in the predominance here of these mosses. 

 Foremost among the sphagnums are the mesophytic cushion- 

 forming species {S. papillosum, S. magellanicum, and vS". 

 piilchrum). Growing in rich profusion, these latter form soft, 

 wet, cushion-like or pillow-like beds which cover the ground 

 almost uninterruptedly over large areas. Other species of 

 Sphagnum, however, are by no means absent. Hollows in the 

 bog proper are commonly occupied by societies of 6'. tcnellum and 

 5". Pylaisei, species which do not form cushions, while on the 

 higher cushions, in greater or less abundance, may grow the 

 relatively xerophytic cushion-forming species. In addition, the 

 small ponds or pools which commonly dot the bog surface (Figs. 

 62, 64, 66, 68, 69) usually contain various aquatic and semi- 

 aquatic species. These ponds constitute one of the most dis- 

 tinctive features of areas occupied by wet bog, but their vege- 

 tation, strictly speaking, belongs in quite a different category 

 from that of the wet bog association-type (see further under dis- 

 cussion of successional relations). 



The surface of a wet bog, viewed in its entirety, may be flat 

 or slightly convex; viewed in detail it is more or less uneven 

 and hummocky. It is commonly underlain by an accumulation 

 of peat from two to four feet in thickness, which consists of an 

 intimate admixture of sphagnum, sedge, and shrub remains. 



The dry hog association-type. — This, the culminating associa- 

 tion-type of the raised bog series, may develop in similar situa- 

 tions to the preceding but particularly or nearly level surfaces, 

 either flat or undulating. In contrast to bog meadow and wet 

 bog, perhaps the most striking features of a dry bog (Figs. 66, 

 69) are its usually convex shape, the luxuriant development of 

 the xerophytic cushion-forming sphagnums {S. fusciim, S. 

 capillacetim tenelluni and S. tenerum), the presence of such 

 xerophytic seed plants as Empetrum, Gaultheria, and Vaccinmm 



