MOSSES WITH A HAND-LENS 



***** 



Fig. 36. Brachythecium rivulare X 1 ; leaves and capsules X 10. 



growing submerged the stems of the Rivulet Brachythecium be- 

 come greatly elongated, slender and sparingly branched, with 

 few and distant leaves. It is always much lighter colored than 

 either the Beaked Water Moss or the Round-leaved Hypnum; the 

 leaves are rather smaller, ovate and obtusely acute. The branch 

 leaves are usually much smaller than the stem leaves. The stems 

 are often tall and stout, with a shrub-like habit. The capsules 

 are not beaked, they mature in autumn. 



Brachythecium plumbsum (Sw. ) B. & S. grows on rocks in 

 the bed of brooks, but is not submerged except at high water. 

 The difference in habit alone is sufficient to distinguish it from 

 B. rivulare, but it is also much smaller, darker green, more 

 closely applied to the substratum, nearly prostrate, with acumi- 

 nate stem leaves. 



B. populeum (Hedw ) B. & S. is a much more slender 

 species growing on boulders, often near streams, but never on 

 stones regularly submerged at high water. In this species the 

 midrib runs to the very apex of the leaf. 



Two other species of Brachythecium are treated elsewhere 

 (pp. 36 and 50). 



