212 BOTANY. 



23, Anthocerotace^), which are terrestrial thalloid plants 



with slender spore-fruits (Fig. 124). 



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 disks, and another pro- 

 duces the female branches, which have lobed disks. Note the brood- 

 cups, with contained brood-masses (gemmae). 



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

 microscope, and note the round breathing-pores. Next strip ofE 

 some of the epidermis, mount in alcohol, and study with a 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 disk, mount in water, and 

 study the antherids (Fig. 133, C). By repeated trials antherozoids 

 may be seen. 



(e) Make similar sections of the female disk, and study archegones. 

 By taking older specimens the spore-fruits, spores, and elaters may 

 be studied. For the latter, mount in alcohol and afterward add a 

 little potassic hydrate. 



(/) 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 leafy Liverwort. In the spring the 

 minute splitting spore-fruits may readily be found. 



Systematic Literature. — Underwood, Descriptive Catalogue of the 

 North American Hepaticae. Gray, Manual of Botany, 703-732. pi. 

 SZ^25 (6th edition). 



Class 10. Musci. The Mosses. 



391. 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. 



392. The tissues of the Mosses present a considerable ad- 

 vance 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 



