196 ELEMENTS OP STRUCTURAL BOTANY. 



346. The Mosses and Liverworts constitute a distinct 

 group of plants called Bryophytes. It will be evident 

 from the preceding descriptions that in the matter of 

 reproduction they do not differ materially from the Pteri- 

 dophytes. They are, however, distinctly separated from 

 them by the simpler organization of their tissues. The 

 Bryophytes have no true roots, but only root-hairs or 

 rhizoids. The whole plant-body is, as a rule, composed 

 of thin-walled parenchyma, and only in a few cases is 

 there any appearance of a development of a fibro-vascu-lar 

 system, and that only of the vaguest possible kind. There 

 is, however, a well-defined epidermal system, and stomata 

 are not uncommon. 



CHAPTER XXIIL 



EXAMINATION OP A MUSHROOM — A LICHEN — A OHABA. 



347. Mushroom. Fig. 246 is a representation of 

 the ComiJion Mushroom of the natural size, while Fig. 

 247 shows the several stages of its growth. At A is seen 

 a matted fibrous mass, which is the underground portion 

 of the plant.' It is called the mycelium; at .several 

 places on it rounded outgrowths of different sizes are 

 visible. These eventually develope into the overground 

 part of the Mushroom. At II is shown a vertical section 

 through one of these outgrowths at an early stage ; at I 

 in this figure you will observe two dark dots ; these are 

 the open ends of a channel which forms a complete ring 



