112 HOW TO KNOW THE MOSSES 



characteristics are the same as those given below. This 

 form of Grimmia may be confused with Rhacomitrium, 

 the following genus, and the pleurocarpous mosses 

 growing on rocks in streams and having the lower 

 part of the stem leafless. See Hygroamhlystegium 

 (p. 21 1). Like all acrocarpous mosses single plants 

 are easily separated, while the pleurocarpous mosses 

 usually form such tangled mats that no great length 

 of the stem can be pulled out. 



Plants growing in rather loose tufts, on rocks; dull olive- 

 green or brownish except at the young tips, which are a 

 brighter green; common; fruit common. 



Stems erect or ascending; usually not more than 

 I inch long, except in var. rivularis; branching 

 somewhat freely; stijff when dry. 



Leaves long and narrow, about five times 

 ^ . . longer than broadest part, sometimes ending in 

 apocarpa a white hair-point giving the plants a hoary ap- 

 Capsule pearance; spreading when moist; closely folded 

 enlarged, -^hen dry; dull olive-green, or brownish. 

 Seta very short, hidden in leaves. 



Capsule almost hidden at the tips of the branches, oval, 

 erect; mature in late spring. 



Operculum short-beaked; bright red, appearing like a red 

 tip to the branch, as the rest of the capsule is so hidden by 

 the leaves. 

 Range, almost cosmopolitan. 



The Grimmias grow in such small dark patches that 

 they do not often attract the eye except after rain, 

 when the leaves are well spread and lighter colored, and 



