LIFE HISTORY OF A LIVERWORT 
211 
In the first two and last of these orders the plant body is a 
thallus, either closely resembling the prothallus of the 
ferns, or freely branching. In the third order the plant 
FIG. 154. A leafy liverwort (Porella namcidaris). Male plant, about 
natural size. (After M. A. Howe.) 
body is leafy (foliose), and in this respect somewhat re- 
sembles certain true mosses, for which it is often mis- 
taken (Figs. 154 and 155). In the first two and last orders 
the thallus always shows dorso- ventral differentiation. 
