130 MOSSES WITH A HAND-LENS 



ecostate. The capsules are not beaked. They mature in July 

 according to Limpricht, but in autumn according to my obser- 

 vations. The Round-leaved Hypnum is frequent in mountain 

 streams, but has formerly been referred to another closely re- 

 lated species (H. molle Dicks.), a much rarer moss with ovate- 

 elliptical leaves. 



There are several other species of Hygrohypnum that may 

 be found in water. One of these (H. ochraceum Turn.) may be 

 recognized by its yellowish or ochre-green color and strongly 

 secund leaves narrowly obtuse at apex and having the costa 

 short and double, or single and half the length of the leaf 

 or mo*. 



AMBLYSTEGIUM IRRIGUUM (Hook. & Wils.) B. & S. is a 

 small moss very much smaller than any of the other Water- 

 loving Hypnums. The leaves are strongly costate to the apex. The 

 peculiarity of this moss is its harsh gritty feeling, which remains 

 after being thoroughly washed. This is, perhaps, the blackest of 

 the four submerged species. The capsules are in good condition 

 in summer; when dry and empty they assume the characteristic 

 Amblystegium pose shown in A. serpens, though they are smaller 

 than in that species. 



BRACHYTHECIUM. 



The Brachytheciums, as previously stated (p. 114), are dis- 

 tinguished by their short thick unsymmetric cernuous capsules, 

 and leaves with a well developed midrib. There are at least two 

 species of Brachythecium that should be classed among the 

 water-loving members of the Hypnum Family, although they are 

 not so thoroughly aquatic as the two species just described. 



B. RIVULARE B. & S., the Rivulet Brachythecium, loves best 

 the wet gravelly soil at the edges of cool swift brooks. Fre- 

 quently it will entirely cover the gravelly bottom of a mountain 

 stream that is nearly dry during the summer. It is submerged at 

 times of high water and never grows in places that become 

 entirely dry ; occasionally it will grow submerged, but even then 

 it is attached to the gravel at the bottom of the stream and not to 

 the stones as in the case of the two preceding species. When 

 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 



