6l6 RELATION TO ENVIRONMENT. 



the bank except some algae and liverworts. On the sides where 

 the forest has been cleared off swale-grasses are growing in the 

 ditch or marginal depression and ground is being slowly built up. 

 1103. Heaths. Heaths or heath-moors are plant societies 

 where heaths are the dominant vegetation. Examples of heaths 

 are huckleberries and bearberries, cranberries (Vaccinium 

 species), but especially members of the Ericaceae, like wild rose- 

 mary (Andromeda), dwarf cassandra (Chamaedaphne = Cassan- 

 dra), heather (Calluna vulgaris), etc. These usually occur in 

 sphagnum-moors (see sphagnum-moors), but sometimes heath 



Fig. 530. 



Heather formation on sand in crevices of rock. Heather (Calluna vulgaris) in 

 the foreground and in rock crevices on the left. At the right a few dwarfed, 

 stunted trees of Pinus sylvestris bent to one side by wind. On rocky hills, coast 

 of Sweden, Botanic Garden, Gothenburg. (Photograph by the author.) 



formations are on sandy ground, which is more elevated and dry, 

 especially the heather (Calluna vulgaris). The heather forms 

 extensive heaths in northwestern Europe either in moors or on 

 dry, sandy ground. It also occurs in northeastern North America, 

 but is rather local. 



1103a. Spruce and tamarack swamps. The black spruce and 

 the larch or tamarack often encroach on the peat-moors, heaths, 

 or muskeags, and make distinct formations. The trees in this 



