MUSCI AND HEPATICAE 



367 



and penetrating deeply into the soil. Such arrangements, both in 

 the vegetative structure of the gametophyte and in the disposal 

 and protection of the sexual organs, suggest that the Liverworts are 

 making the best of subaerial life, to which their simple structure 

 is not in itself well suited. Their fertilisation is by movement of 

 spermatozoids motile through water. 



B 



V. 



FIG. 311. 



A = archegonium of Riccia trichocarpa, showing ventral canal cell (v) and ovum. ( x 525). 

 B=ripe archegonium of Riccia glauca. (xa6o). (After Campbell.) 



The sporogonium itself is on a simpler scale than that of the Mosses. 

 Excepting the peculiar group of the Anthoceroteae, it does not carry 

 on photo-synthesis, nor is there any complete columella. Moreover 

 the sporogonium is longer enclosed in the archegonial wall ; but it 

 bursts it at maturity, when the seta elongates, bearing outwards the 

 spherical head. There is no operculum, but the relatively thin wall 

 bursts, usually into four valves, and the spores, interspersed among 

 fibrous elaters that help to distribute them, are exposed as a flocculent 

 mass to the breeze, and are scattered in the dry state. Though the 

 details are different from those of the Mosses, the end is the same 

 (Fig. 312). 



