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 Musci 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, chiefly 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 Sporophyte 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 them and 

 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 fixes itself 

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