474 



BOTANY OF THE LIVING PLANT 



the leaves may be divided into narrow laciniae, which collectively hold 

 water as in a sponge. Thus it appears there is a wide scale of 

 adaptation of the gametophyte in Liverworts. Its results offer 

 analogies with the special adaptations seen in the sporophyte of 

 Flowering Plants. 



The sexual organs are essentially similar to those of the Mosses ; 

 but there are differences in their segmentation. This suggests that 



Fig. 370. 



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

 B = ripe archegonium of Riccia glauca. ( x 260.) (After Campbell.) 



their origin may have been distinct. In the thalloid Liverworts they 

 are always borne on the morphologically upper surface ; but by 

 various means they are carefully protected, being sometimes sunk 

 deeply in the thallus (Fig. 370). . In the Jungermanniae they are 

 covered in by envelopes, the number and variety of which give useful 

 features in classification. A particular interest attaches to those 

 which develop a " marsupium," that is a nursing-sac surrounding the 

 archegonia, and penetrating deeply into the soil. Such arrangements, 

 both in the vegetative structure of the gametophyte and in the 



