56 MOSSES. 



We will now examine a few common mosses more 

 in detail, beginning with the ACROCARPI. 



Sphagnum acutifolium (PI. III. fig. 4) is found in 

 pools or bogs, growing at the margins so as "to be 

 partially immersed. In this moss, the upper branches 

 are grouped into a head. The leaves are crowded, 

 and overlapping or im'bricate (imbrex, a tile) on the 

 elongate stems; they are egg-shaped (ovate) on the 

 main stems (fig. 1), and narrower or ovate-lanceolate 

 on the branches; they are nerveless, and finely 

 toothed at the apex. The capsule (fig. 5) is roundish- 

 ovate, without a peristome, and the operculum is 

 flattened. The grouped arrangement of the upper 

 branches renders the species of Sphagnum easily re- 

 cognized. The structure of the leaves is also very 

 peculiar and characteristic (fig. 2) . The cells of which 

 they consist are of two kinds, one (fig. 2 a) being 

 colourless, elongate, pointed, and containing a spiral 

 fibre ; the other consisting of shorter and narrower 

 obtuse cells, containing chlorophyll, and situated be- 

 tween the former. In many of the former kind of 

 cells, little round apertures exist on the under surface, 

 and minute animals may sometimes be found im- 

 prisoned in them. 



Another species of Sphagnum, S. obtusifolium, is 

 common, and greatly resembles the above, but has 

 shorter and thicker stems, and rounded-ovate, very 

 concave, and obtuse leaves. 



Gymnos'tomum truncat'ulum (PL III. fig. 6) is a 

 common little moss, found on banks and in fields 

 and gardens. 



In this there is no peristome, although, in the 

 young condition, a membrane extends more or less 

 over the interior of the mouth of the capsule. The 

 stem is slender, rigid, and simple, or but little 

 branched. The calyptra is dimidiate ; the operculum 

 is present (fig. 8), and terminates above in an oblique 

 beak, or it is obliquely rostrate (ros'trum, a beak) as 



