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 
Fre. 123._. 'Wo rows of teeth (the peristome) of which 
Sporophytes there may be 4, 8, 16, 32 or 64. Here 
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- 
merum), Wood Mosses (Bryaceae and Mnia- 
ceae), Humpback Mosses (Buaxbaumiaceae), 
and Hair-cap Mosses (Polytrichaceae). Among To} . mae 
the Side Mosses are the Brook Mosses (Fon- * pe = 
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). 
(b) 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. 
