12 MOSSES AND FERNS chap. 



the archegonia. In the thallose Hepaticae, both antheridia 

 and archegonia are generally enclosed by a sort of capsule, 

 similar to the perichsetium of the foliose forms formed by the' 

 growth of the tissue of the thallus immediately surrounding 

 them. 



The Asexual Generation 

 {Sporophyte, Sporophore, Sporogoniuni) 



The sporophyte of the Muscineae is usually known as the 

 " sporogonium," and, as already stated, never becomes entirely 

 independent of the gametophyte. After the first divisions are 

 completed there is at an early period, especially in the 

 Hepaticae, a separation of the spore-producing tissue or arche- 

 sporium, all the cells of which may produce spores, as in Riccia 

 and the Mosses, or a certain number form special sterile cells 

 which either undergo little change and serve simply as nourish- 

 ment for the growing Sphcerocarpus, or more commonly assume 

 the form of elongated cells, — elaters, which assist in scattering 

 the ripe spores. 



Classification 

 Class I. Hepatic(B {Liverworts) 



The protonema is either rudimentary or wanting, and not 

 sharply differentiated from the gametophore. The game- 

 tophore is, with the exception of Riella Haplomitrium and 

 Calobryum, strongly dorsiventral, and may be either a (usually 

 dichotomously) branched thallus or a stem with two or three 

 rows of leaves. Non-sexual multiplication of the gametophyte 

 by the separation of ordinary branches, or by special reproductive 

 bodies, gonidia {Aneura tnultifidd) or gemmae — (many foliose 

 Ju7igerinanniacece, Blasia, Marchantia, etc.). The sporogonium 

 (except in Anthocerotese) remains within the enlarged venter 

 (Calyptra) of the archegonium until the spores are ripe. Before 

 the spores are shed the sporogonium generally breaks through 

 the calyptra by the elongation of the cells of the stalk or seta. 

 All the cells of the archesporium may produce spores, or part 

 of them may produce sterile cells or elaters. 



