LEAFY LIVERWORTS 



121 



like head, between the radiating ribs. Reboulia, common on 

 road banks, resembles the three preceding plants in general 

 appearance, but the thallus is narrower and thicker and the 

 network of lines on the upper surface is less distinct. Its fruit- 

 head is hemispherical in form. 



Besides the ribbon-like liverworts, there are leafy liverworts, 

 forming, in fact, the greater part of this group of plants. It 

 is a little difficult at first to distinguish some of the leafy liver- 

 worts from the mosses, among which they often grow, but they 



FIG. 33. Radula. A, upper side of plant with two fruits ; B, part of 

 under side of a plant, magnified. 



are generally more delicate plants, and their thin transparent 

 leaves are always arranged in two side rows on the slender stem, 

 sometimes with a third row on the under side. Some of them 

 have the leaves divided into two lobes, which is never the case with 

 the mosses. The kinds shown in Figs. 32-36 are all very common, 

 and occur in most places, especially beside streams. It will be 

 noticed that their fruits resemble that of Pellia, the capsule 

 opening by four valves. 



Very few of the leafy liverworts are able to endure drought, 



