188 BOTANY. 
mostly leafy creeping plants growing on moist earth, rocks, 
and tree-trunks. 
Practical Studies.—(a) Collect specimens of the Common Liverwort, 
which may be found in fruit in midsummer. Note that one plant 
produces the male branches, which have flat discs, and another pro- 
duces the female branches, which have lobed discs. Note the bud- 
cups, with contained buds (gemme), 
(6) Examine the upper surface of a plant with a low power of the 
microscope, and note the round breathing-pores. Next strip off some 
of the epidermis, mount in alcohol, and study with high power. 
(c) Make longitudinal sections of the plant through its thickened 
central rib, and observe the elongated cells, which foreshadow fibro- 
vascular bundles. 
(d) Make vertical sections of the male disc, mount in water, and 
study the antherids (Fig. 102, C). By repeated trials, antherozoids 
may be seen. 
(e€) Make similar sections of the female disc, and study archegones. 
By taking older specimens, the spore-fruits, spores, and elaters may be 
studied. For the latter, mount in alcohol and afterwards add a little 
potassic hydrate. 
(f) Examine the bark of trees for small brownish Scale-mosses. 
Mount a bit of one in alcohol, afterwards adding potassic hydrate, 
and study as a specimen of a Jeafy Liverwort. In the spring the 
minute splitting spore-fruits may readily be found. 
Cuass II. Musctr (the Mosses). 
398. The adult plant-body in this class is always a leafy 
stem, which is rarely bilateral. It is fixed to the soil or 
other support by root-hairs (rhizoids) which grow out from 
the sides of the stem, but there are no true roots. The 
leaves are usually composed of a single layer of cells, and 
sometimes have a midrib. 
394. The tissues of the Mosses present a considerable 
advance upon those of the Liverworts. In the stem there 
is frequently a bundle of very narrow thin-walled cells, 
which in some species become considerably thickened. In 
a few cases there have been observed bundles of thin-walled 
