VEGETATION OF ROCKY PLACES. 



617 



situation are usually of slow growth. The under vegetation 

 consists of shrubs, herbs, and mosses like those on the moors 



Dying black spruce in moor. Note the abundance of cotton-grass (Eriopho- 

 rum). (Photograph by the author.) 



described in paragraphs 1090-1093. In open places, or in 

 moors where the spruce is dying because of fires or floods, the 

 cotton-grass is often abundant, as shown in fig. 531. This grass 

 also occurs on other moors. 



1104. Cane-swamp societies. These are frequent in the 

 Southern States in low ground along streams, and are formed 

 by a dense growth of the cane, Arundinaria. 



1105. Salt-marsh societies. These are formed along the salt 

 shores of the ocean or of salt lakes, where the gradient of the 

 shore is low and the soil is nitrophytic. The water is brackish 

 and varies in its salt content according to the relation of the 

 marsh to the sea and to the run-off from the land. The seed 

 plants are rooted in the soil, which is either very wet with the 

 brackish water, or entirely submerged, and the plants also more 



