CHAPTER XI. THE BRYOPHYTA. 



343 



usually ruptures at the base, and is carried up as a calyptra on 

 the top of the capsule. In the great majority of cases the latter 

 has a circumscissile dehiscence, and the operculum comes off 

 like a lid. The columella is always present, and the capsule 

 never produces elaters. 



There are three orders of Mosses, as follows : 

 (A) The Sphagnaceae or Bog-mosses, grow in tufted 

 masses in boggy places, about springs and along the banks of 

 mountain brooks, where the supply of water is constant ; they 

 have a pale-green, or sometimes a purplish color, straight stems, 

 with numerous laterally spreading, fascicled branches, which are 

 covered with closely imbricated leaves. The latter are nerve- 

 less and consist of a single layer of cells, but these are of two 

 kinds, one large, colorless, perforated by pores and lined with 

 spiral or annular filaments, and the other narrowly linear, chlo- 

 rophyll-bearing, and forming a net-work around the former kind. 

 The antheridia are borne on club-shaped or catkin-like, usu- 

 ally colored branches, and the 

 archegonia are commonly in 

 groups of three or four enclosed 

 in a bud-like involucre at the 

 ends of short branches. The 

 capsule is round and opercu- 

 lated, but without a peristome, 

 B and pedicelled, but the pedicel, 

 instead of being a part of the 

 sporogonium, as is usually the 

 case in other mosses, is a pro- 

 longation of the axis of the 

 sexual plant. The remains of 

 the archegonium are found at 

 the base of the capsule, and 

 not as a cap or calyptra at the 

 top. 



Fig. 552. — Sphagnum cymbifolium. A, mature plant-bearing leafy branches, br. and 

 capsules, =. B, one of the capsules, considerably magnified, showing operculum; c, is the 

 remnant of the wall of the archegonium. 



The Sphagnums are the peat-forming mosses, and are largely 

 confined to the cooler portions of the globe. One of these 

 mosses is illustrated in Fig. 552, A and B. 



