TIIK BRYOP/IVTA 317 



selves constitute^ Init a vcny small portion of the sporophytc asa 

 whole, 



2. Jungermatinhiles or Leafy Liverworts. — In number of 

 species this order is by far the largest of the three groups of 

 liverworts. Its thallus is much less complex internally than 

 that of the Marchantiales. Externally, however, it is more 

 specialized, for in most species it is divided into a slender axis 



Fig. 191. — Anthoceros. Portion of thallus, showing several sporophytes, one of 

 which is splitting open and liberating the spores. 



or stem and three crowded rows of small and delicate lobes 

 or "leaves" (Fig. 190). The stem never rises to an erect position 

 but is always prostrate on the ground, to which it is attached by 

 rhizoids. Sex organs are borne on the main axis or on short 

 lateral branches. The sporophyte develops a much longer 

 seta than in the Marchantiales and the spore case contains still 

 more sterile tissue. At maturity it breaks open into four spread- 

 ing lobes. 



3. Anthocerotales. — The gametophyte in this grouji is a simple, 

 flat thallus (Fig. 191), but the sporophyte is remarkable in several 

 particulars. In the genus Anthoceros, the best known member of 

 the order, the sporophyte (Fig. 192) is long and slender and is 



