CHAPTER XXII. 



LIVERWORTS (HEPATIC^). 



306. We come now to the study of representatives of another 

 group of plants, a few of which we examined in studying the organs 

 of assimilation and nutrition. I refer to what are called the liver- 

 worts. Two of these liverworts belonging to the genus riccia 

 are illustrated in figs. 58, 171. 



Riccia. 



307. Form of the floating riccia (R. fluitans). — The gen- 

 eral form of floating riccia is that of a narrow, irregular, flattened, 

 ribbon-like object, which forks repeatedly, in a dichotomous 

 manner, so that there are several lobes to a single plant. It 

 receives its name from the fact that at certain seasons of the year 

 it may be found floating on the water of pools or lakes. When 

 the water lowers it comes to rest on the damp soil, and rhizoids 

 are developed from the under side. Now the sexual organs, and 

 later the fruit capsule, are developed. 



308. Form of the circular riccia (R. crystallina). — The 

 circular riccia is shown in fig. 171. The form of this one is quite 

 different from the floating one, but the manner of growth is much 

 the same. The branching is more compact and even, so that a cir- 

 cular plant is the result. This riccia inhabits muddy banks, 

 lying flat on the wet surface, and deriving its soluble food by 

 means of the little rootlets (rhizoids) which grow out from the 

 under surface. 



Here and there on the margin are narrow slits, which extend 



140 



