188 BOTANT. 



mostly leafy creeping plants growing on moist earth, rocks, 

 and tree-trunks. 



Practical Studien. — (n) Collect specimens of the Common Liverwort, 

 which may be found in fruit in midsummer. Note that one plant 

 produces tlie male branches, which have flat discs, and another pro- 

 duces the female branches, which have lobed discs. Note the bud- 

 cups, with contained buds (gemmse). 



(/>) Examine the upper surface of a plant with a low power of the 

 microscope, and note tlie round breathing-pores. Next strip off some 

 of the epidermis, mount in alcohol, and study with high power. 



(c) Make longitudinal sections of tlie plant through its thickened 

 central rib, and observe tlie 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. 



(/) Examine the bark of trees for small brownish Scale-mosses. 

 Mount a bit of one in alcoliol, afterward^ adding potassic hydrate, 

 and study as a specimen of a leafy Liverwort. In the spring the 

 minute splitting spore fruits may readily be found. 



Class II. Musci (the Mosses). 



393. 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 



