252 PHYLUM VIII. BRYOPHYTA 



of cases the species live in the water. They are undoubt- 

 edly the highest of the class, and show a greater differ- 

 entiation of tissues than either of the pre- 

 ceding orders. The spore-cases usually 

 open by a circular lid (operculum), and 

 the opening is usually guarded by one or 

 two rows ^ teet h (* ne peristome) of which 



the seta is a part of the sporophyte. 

 448. There are more than fifty families of True 

 Mosses, of which about one-half are Top Mosses 

 (Acrocarpi), i.e. bearing their sporophytes at the summit 

 of the gametophyte stem, the remainder being Side 

 Mosses (Pleurocarpi}, with laterally borne sporophytes. 

 Among the first are Turf Mosses (Dicranaceae) , Cushion 

 Mosses (Leucobryaceae) , Petticoat-mosses 

 (Splachnum), Bristle Mosses (Funariaceae 

 and Timmiaceae), Ephemeral Mosses (Ephe- 

 merwri), Wood Mosses (Bryaceae and Mnia- 

 ceae), Humpback Mosses (Buxbaumi&ceae) , 

 and Hair-cap Mosses (Polytrichaceae). Among Top ' mos ^ 

 the Side Mosses are the Brook Mosses (Fon- 

 tinalaceae), the Tree Mosses (Climaciaceae) , and the Bog 

 Mosses (Hypnaceae). 



Laboratory Studies, (a) Collect several kinds of mosses in 

 fruit; some of these should be of large species. Note the 

 brownish root-hairs, the stem and leaves, the spore-fruit (sporo 

 phyte) composed of a slender stalk (seta) bearing a spore-case, 

 the latter in some species covered by a membranous or hairy 

 cap (calyptra). 



(6) Select a broad-leaved species. Mount a single leaf in 

 water, and examine with a lower power. Note that the leaf 

 is (generally) a single layer of cells, and that the midrib (if 

 present) is composed of elongated cells. Make cross- and 

 longitudinal sections of stems of the larger species, and note 

 that some of the cells are elongated and fiber-like. 



