CHAPTER XVI 

 MOSSES AND LIVERWORTS (BRYOPHYTES) 



241. Introductory statement. There are two classes of this 

 division of the plant kingdom, the mosses (Musci) and liver- 

 worts (Hepaticce). The name Bryophytes means " moss plants." 

 Liverwort literally means " liver plant" or " liver root," so 

 called from the supposed resemblances in form between the 

 liverwort plants and the .human liver. There is a rather com- 

 mon flowering plant (Ifepatica) which is sometimes called 

 liverleaf or liverwort. This flowering plant should not be con- 

 fused with the true liverworts. Also there is a common habit 

 of calling all small green plants "mosses," but when we dis- 

 cover what kind of plants mosses are, we shall find the proper 

 use of this term. 



In some respects liverworts are simpler than the mosses, 

 and they are given as the first or lowest class. But it;is so 

 much easier to get clear notions of some aspects of bryophytes 

 by a study of mosses that we shall first consider them. 



MOSSES 



242. The moss plant: the protonema. Mosses of various 

 kinds are widely distributed. Careful observation of a moss 

 plant enables one to see that it has green leaf-like structures 

 arranged around a very small stem. Sometimes also there ap- 

 pears upon this leafy stem a slender stalk with a swollen pod- 

 like tip or capsule (Fig. 216). In this tip are many simple 

 asexual spores, and we shall begin the life cycle by following 

 the germination of one of them. 



When an asexual spore germinates there grows from it a 

 filamentous, branching body. Its cells contain chloroplastids 



257 



