Vegetation of Northern Cape Breton. 



349 



formation, but little change would appear to have taken place 

 at any time since their formation. 



Geological and other factors influencing the distribution and 

 vegetation of inland lakes. — The majority of the lakes and ponds 

 in the lowland of northern Cape Breton are glacial : they occupy 

 depressions which have resulted from glacial activity (see 

 further discussion in Nichols '15, pp. 170-171). In calcareous 

 districts, however, particularly in localities where there are 



Figure 41. — Freshwater Lake, South Bay, Ingonish ; cut off from ocean 

 by a shingle beach ; in distance, Middle Head, mostly granitic ; in right 

 foreground, a gypsum outcrop; second growth forests of white spruce 

 and balsam fir. Photograph by Dr. L. H. Harvey. 



extensive deposits of gypsum, "sink holes" due to subterranean 

 erosion are common, and these frequently are occupied by ponds. 

 Still a third type of water basin, due entirely to vegetative 

 activity, is encountered on the plateau, and will be described in 

 some detail later. 



In their influence on the vegetation of lakes and ponds, drain- 

 age and permanency are factors of considerable significance. 

 The effect of drainage will be discussed presently in connection 

 with the formation-types of swamps. The effect of permanency 

 is seen in comparing the vegetation of permanent, with that of 



