MOSSES WITH A HAND-I,ENS 



131 



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, and are 

 slenderly pointed. If the stem leaves be carefully removed and 

 mounted the alar cells will be seen to be quite appreciably larger 





Figure 65. Brachytheciuni rivulare X i; leaf and capsules X 10. 



than the others, although not so markedly so as in the Common 

 Hypnum. The stems are often tall and stout, with a shrub-like 

 habit. The capsules are not beaked and mature in autumn. If 

 the seta be examined with a. high power lens it will be seen to be 

 covered with fine papillse throughout. 



B. PLUMOSUM (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; it is much smaller, darker green, more closely applied 

 to the substratum, nearly prostrate, with acuminate stem leaves. 

 The seta is papillose in the upper portion only. 



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, and the seta is papillose 

 in the upper part only. 



