Vegetation of Northern Cape Breton. 



431 



establishes itself and with 5. piilchrum, which is already present, 

 rapidly builds up the surface to a height of a foot or more above 

 water, at which level S. fuscum begins to assert itself. In this 

 way there arises a typical bog (Fig. 63), in which the cushion- 

 forming sphagnums and their customary vascular associates pre- 

 vail. Locally, however, the low mat is usurped by Sphagnum 

 Pylaisei. This sphagnum, it should be remarked, while it grows 

 profusely in many small undrained ponds, is seldom a conspicu- 



FiGURE 63. — A characteristic bog in the mountains west of Ingonish : 

 sedges, ericads, and sphagnums predominant, with scattered clumps of 

 black spruce. 



ous element of the aquatic vegetation in ponds of any size, like 

 the present one, especially where they are well drained. But it 

 frequently occurs in the swamps which border them. Along 

 with 6^. Pylaisei commonly grows the liverwort, Cephalocia 

 fluitans. These two bryophytes, as elsewhere suggested, tend to 

 form a rather compact, felty growth over the substratum, which 

 seems in some inexplicable manner to hinder the invasion of 

 these areas by the cushion-forming sphagnums. So tenaciously, 

 indeed, may they hold their own that, as the contiguous higher 



