SECTION 17.] 



BRYOPHYTES. 



163 



form, Bryum being the 



principal kiml> . true 

 plural- , and Hepatic 



to attach them to the soil, or to trunks, or to other bodies on which they 

 grow. Plants of this grade arc chiefly Mosses. So as a whole they take 



the name of 



498. Bryophyta, Bryophytes in Englis 

 Greek name of a Moss. These plants are of two 

 Mosses (M/tsci, which is their Latin name in the 

 Mosses, or Liverworts (Hepatica). 



499. Mosses or Musci. The pale Peat-mosses (species of Sphagnum 

 the principal component of sphagnous bogs) and the strong growing Hair 

 cap Moss (Polytrichum) are among the lar- 

 ger and commoner representatives of this 

 numerous family ; while Fountain Moss (Fon- 

 tinalis) in running water sometimes attains the 

 length of a yard or more. On the other hand, 

 some are barely individually distinguishable 

 to the naked eye. Fig. 527 represents a com- 

 mon little Moss, enlarged to about twelve 

 times its natural size ; and by its side is part 

 of a leaf, much magnified, showing that it is 

 composed of cellular tissue (parenchyma-cells) 

 only. The leaves of Mosses are always sim- 

 ple, distinct, and sessile on the stem. The 

 fructification is an urn-shaped spore-case, in 

 this as in most cases raised on a slender stalk. 

 The spore-case loosely bears on its summit 

 n thin and pointed cap, like a candle-extin- 

 guisher, called a Cah/ptra. Detaching this, it 

 is found that the spore-case is like a pyxis 

 (370), that is, the top at maturity comes off 

 as a lid {Operculum) ; and that the interior is 

 filled with a green powder, the spores, which 

 are discharged through the open mouth. In 

 most Mosses there is a fringe of one or two •! (/s/l.nV^/s 

 rows of teeth or membrane around this mouth 628 52 ' 

 or orifice, the Peristome. When moist the peristome closes hygrometri- 

 cally over the orifice more or less; when drier the teeth or processes 

 commonly bend outward or recurve; and then the spores more readily es- 

 cape. Tn Hair-rap Moss a membrane is stretched quite across the month, 

 like a drum-head, retaining the spores until this wears away. See Figures 

 527-541 for details. 



500. Fertilization in Mosses is by the analogues of stamens and pistils, 

 which are hidden in the axils of leaves, or in the cluster of leaves at the 



Fro. 527. Single plant of Physcomitrium pyriforme, magnified. 02*. Top of * 

 leaf, cut across; it consists of a single layer ol cells. 



