ix.] ABOUT MOSSES AND LICHENS. 145 



have distinct stem and leaves, like the mosses, though 

 the leaves are of a more delicate texture, and lack 

 the mid-rib which many of the mosses possess. The 

 germination of the spores is similar to that of mosses. 

 The Liverworts (Marchantiacece) have no distinct 

 stem or leaves, but consist of a flat, horizontal 

 cellular frond, attached by tiny rootlets from the 

 under surface. There are but nine British species, 

 the most plentiful of which is the Common Liver- 

 wort (Marchantia polymorphd], which will serve to 

 illustrate the order. It is very common in all moist 



FIG. no. 

 FIG. 109. 



situations, its dull green fronds covering patches of 

 earth. The organs of reproduction are borne upon 

 stalks. The antheridia and archegonia are produced 

 on separate plants. The antheridia receptacle is 

 shown in fig. 109. It is slightly concave on the upper 

 surface, and studded with the openings of the anther- 

 idia, which are embedded in its substance (fig. 1 10, 

 section). They contain the antherozoids, which, on 

 being set free, enter and fertilise the archegonia, 

 which give rise to the sporangia shown in fig. in. 

 The spore cases are arranged on the under surface 



K 



