290 



THE BRYOPI1YTES 



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formations of many regions. The peat mosses are the chief in- 

 habitants of certain kinds of bogs and pond margins. The mosses 



therefore constitute a group of 

 considerable importance in the 

 ^* plant population of the earth, while 

 the liverworts are for the most 

 part confined to rather special 

 life habits and, with the exception of the 

 leafy liverworts, are not rich in species or 

 numerous in individuals. Almost all of the 

 mosses fall into two groups, which may be 

 called the peat mosses and the common mosses. 



292, The peat mosses. The peat mosses (order 

 tipltagnales) are very remarkable for their struc- 

 ture and life habits. There is only a single genus, 

 Sphagnum, with about two hundred and fifty 

 species. The plants (gametophytes) have long 

 stems, with delicate, leafy branches, some of 

 which grow downward and soak up water, while 

 the rest form a dense cluster at the top (Fig. 259). 

 The peculiar structure of these mosses allows 

 them to absorb and hold water like a sponge, for 

 which reason they are used by gardeners for 

 packing around plants and flowers. The dried 

 rnoss is sometimes used for bedding in stables. 

 The sexual organs (antheridia and archegonia) 

 are formed very* early in the spring or in the 

 late winter, and the fertilization of the egg 

 leads at once to the development of a sporophyte. 

 The peat moss The sporophytes are large, smooth capsules (Fig. 

 (Sphagnum) 2 60, J), which appear to have stalks, but these 

 are really special developments of the gametophytes. The spore 

 case is attached to the top of the stalk by a large foot and opens 

 by a cover (Fig. 260, 7?, c}, which falls off. The spores on ger- 

 mination produce small flat cell plates, out of which the leafy 



FIG. 25U 



