2IO 



STRUCTURE AND LIFE HISTORIES 



in little pits or depressions on the upper surface. The 

 habitat of the Hverworts illustrates a step forward in the 

 abandonment by plants of a wholly aquatic Hfe and the 

 establishment of a land vegetation; but the prevailingly 

 moist situations in which most of the species are found, 



Fig. 153. — Anthoceros fimhriatus. Portion of a thallus viewed from 

 below, with the rhizoids omitted. The one-layered crisped lobes at the 

 margin serve to retain moisture. (After Goebel.) 



and the need of water for fertilization by swimming 

 sperms (soon to be described), points to an ancestral 

 habitat truly aquatic. 



193. Description of the Plant Body. — The plant body 

 of the liverworts shows a marked departure from that of 

 the mosses in the direction of simplicity. There are four 

 main groups or orders of Hepaticae, as follows: 



I I. Ricciales. 



TT 4.' J 2. Marchantiales. 

 Hepaticae \ 



3. Jungermanmales 



. 4. Anthocerotales. 



i 



