DIVISION IV. 

 BRYOPHYTA. 



CHAPTER XXII. 



MUSCI AND HEPATICAE: MOSSES AND LIVERWORTS. 



The Bryophytes include two Classes, represented by very numerous 

 species, widespread in all lands except in those of persistent drought. 

 They are the Miisci or Mosses^ and the Hepaticae or Liverworts. 

 These form a very natural alliance, and indeed are distinguished from 

 one another only by minor characters. Everyone knows the general 

 appearance of Mosses, as low-growing leafy plants, chiefiy found in 

 moist surroundings. But Liverworts, with a similar habitat, have 

 commonly a flattened form, sometimes without obvious leaves, 

 described as a thallus. Thus the Bryophytes may be either leafy or 

 thalloid. 



All the Bryophytes show a cycle of life of the same general plan as 

 that of the Pteridophytes, having like them two alternating genera- 

 tions. The chief difference lies in the proportions and behaviour of 

 these two phases. It has been seen in Ferns how the Sporophytc has 

 obtained a firm hold on the Land, where it is rooted, and leads an 

 independent life as the " Fern Plant," while the prothallus or game- 

 tophyte is relatively small. But in all the Bryophytes, that green and 

 often leafy structure which is recognised as the "Moss or Liverwort- 

 Plant " turns out on examination to be the gametophyte. It bears the 

 sexual organs, while the sporophyte, which is produced from tlicni ant! 

 bears the spores, is the well-known Capsule, or Sporogonium (Fig. 296). 

 In all the Bryophytes the spore-bearing generation is dependent upon 

 the gametophyte throughout its existence. It never fiv- "-'h' 



