FIELD BOOK OF PONDS AND STREAMS 



is green and the lower one bears root-like outgro\\i;hs. There 

 are but few aquatic liverworts, commonest among them being 

 the Riccias (Fig. 52) which grow in ponds. 



1 - ^ 



Fig. 52. — I, Riccia natans; 2, Riccia fluitans. 



Crystalworts, Riccia fluitans and Riccia natans. — These sim- 

 ple liverworts float free in the water or grow on the mud along 

 the shores of ponds or quiet streams. Riccia natans (Fig. 52) 

 has a lobed thallus and floats on the surface of the water like 

 duckweed. Riccia fluitans (Fig. 52) lies just below the sur- 

 face, spreading its slender branched thallus through the water 

 in a bright green network. It often grows among the duck- 

 weeds and broken bits of its thallus are often caught with 

 net sweepings in the shallows. In case the water in which 

 they are living dries away, either of these Riccias will grow 

 on damp soil and then the thallus is apt to be reddish or pur- 

 plish. Riccias thrive in aquaria and Riccia fluitans is very 

 often a stock plant of supply dealers. 



Mosses — Musci 



Mosses can live on the faces of rocks where food and water 

 are scarce, on decaying logs in deep woods, in marshes, and 

 even completely submerged in brooks and shallow ponds. 

 They grow crowded together like the liverworts and lichens 

 with which they are very commonly associated. But their 

 flat green leaves distinguish them from both liverworts and 

 lichens, neither of which bear leaves. The aquatic Riccias 



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