Vegetation of Northern Cape Breton. 443 



The cushion-forming species of sphagnum are usually incon- 

 spicuous, although the substratum beneath the grasses and sedges 

 is commonly carpeted, at least locally, with Sphagnum Pylaisei 

 and S. tenelhim, together with the liverwort, Cephalozia fluitans. 

 The ground is covered by a firm turf, beneath'which there usually 

 is a layer of peat from a few inches to a couple of feet in depth. 

 The peat is quite compact, consisting very largely of the remains 

 of sedges and grasses, but usually with a matrix of sphagnum 

 remains. The surface of the swamp is flat or undulating; it 

 is relatively smooth, and not hummocky. Slight depressions in 

 the substratum are frequent, and in some of these water may 

 accumulate temporarily to the depth of a few inches, but there 

 are few if any ponds of the sort to be described as characteristic 

 of wet bogs. In addition to the three shrubs named above, 

 Kalmia polifolia, Vacciniiim macrocarpon, and V. Oxycocciis are 

 commonly present, the two latter, as well as the species 

 starred (*) in the subjoined list, being more characteristic of the 

 depressions, particularly where, as is commonly the case, 

 Sphagnum Pylaisei and Cephalozia form a more or less con- 

 tinuous, felty ground cover. Additional herbaceous vascular 

 plants commonly met with in bog meadows are as follows : 



Schisaea pusilla* Drosera longifolia* 



Lycopodium inundatum* Drosera rotundifolid^ 



Eriophorum virginicum Bartonia iodandra* 



Carex oligosperma* Utricularia cormita* 



Carex exilis Solidago uliginosa 



Hahenaria clavellata Aster nemoralis 



Sarracenia purpurea Aster radula 



The vegetation of the shallow depressions just referred to 

 should perhaps be regarded as constituting a distinct association- 

 type, but for convenience they are included here merely as a type 

 of society. 



The zuct hog association-type. — This is commonly developed 

 in situations similar to those indicated for the preceding type, 

 but conditions are most favorable where the surface slope is slight 

 and where the presence of shallow depressions or approximately 

 horizontal surfaces affords habitats which are congenial to the 

 local growth of the mesophytic cushion-forming . sphagnums. 

 The influence of topography is suggested by diagram C of Fig. 



