[Chap. XLVIII MOSSES AND LIVERWORTS 643 



soon form patch-like communities in many kinds of situations. On the 

 basis of their habitat relations, they are conveniently classified ( 1 ) as 

 suspended, attached, and floating species in quiet water, (2) as species 

 anchored in running water, (3) as plants on wet or dry fallen logs, 

 soils, and rocks, (4) as epiphytes on bark and leaves, (5) as bog species, 

 and (6) as pioneers on calcareous and non-calcareous rock surfaces. 



Bryophytes are either annuals or perennials. It is difficult to estimate 

 the age of the perennials, since they have no annual rings or bud scars. 



Fig. 296. The juniper hair-cap moss {Fohjtrichuin) . The male branches may 

 be recognized by their terminal rosettes of broad scales. Photo by E. S. Thomas, 

 Ohio State Museum. 



Annual stem segments are recognizable, however, in some moss plants, 

 such as Polytrichiim ( Fig. 296 ) , in which a characteristic rosette of per- 

 manent leaves surrounds the terminal male reproductive structures. Each 

 year a new stem segment grows from near the center of the terminal 

 rosette of the previous stem segment (Fig. 297). Polytrichum plants 

 have been found in bogs, with 1 to 3 upper live segments and 4 to 8 dead 



