BRYOPHYTES 



III 



istic of the swampy regions of higher latitudes, where they often fill up 

 bogs and form peat, whence they are often called peat mosses. 



Gametophyte. The gametophyte begins as a filament (fig. 242), 

 and then by means of an apical cell with two cutting faces develops 

 as a simple flat thallus with rhizoids (fig. 243), just as in the simpler 

 liverworts. The moss character appears 

 in the development from this liverwort- 

 like thallus of an upright leafy branch 

 (fig. 243). This radial leafy branch, 

 from a dorsiventral body, is called vari- 

 ously the adult shoot, the gametophore, 

 or simply the leafy branch. The name 

 gametophore is used because this branch 



FIGS. 242, 243. Sphagnum: 242, 

 young gametophyte, showing the filament 

 arising from the spore, a rhizoid, and 

 the thallus beginning to develop by an 

 apical cell ; 243, mature thallus, with 

 rhizoids, producing leafy branches. 

 After SCHIMPER. 



244 



FlGS. 244, 245. Sphagnum: 244, sur- 

 face view of cells of leaf, showing the 

 narrow elongated cells (c) containing 

 chloroplasts, and the less numerous hya- 

 line cells (A) with pores (/>); 245, por- 

 tion of cross section showing same 

 features. 



bears the sex organs, just as in Marchantia the sex organs are borne 

 on erect but leafless branches. 



The leafy branch develops by means of an apical cell with three 

 cutting faces, and hence there are three vertical rows of leaves. These 

 branches are densely leafy and profusely branching, forming terminal 

 tufts (fig. 246). 



