12 MOSSES AND FERNS CHAP. 



the archegonia. In the thallose Hepaticse, 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 

 (Sporophytc, Sporophore, Sporogonium) 



The sporophyte of the Muscinese 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 

 Hepaticse, 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 spores, as in Sph&rocarpus, or more 

 commonly assume the form of elongated cells, elaters, which 

 assist in scattering the ripe spores. 



CLASSIFICATION 

 CLASS I. Hepatic a? (Liverworts) 



The protonema is either rudimentary or wanting, and 

 usually not sharply differentiated from the gametophore. The 

 gametophore is, with the exception of Haplomitrium and Calo- 

 bryum, strongly dorsi ventral, 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 reproduc- 

 tive bodies, gonidia (Aneura multifida) or gemmae (many 

 foliose Jungermanniacese, Blasia, Marchantia, etc.). The 

 Sporogonium (except in Anthocerotes) 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. 



