BRYOPHYTA 



177 



archegonium. On the whole, they are a primitive group, with a simple 

 gametophyte and a sporophyte only slightly more advanced than that of 

 Riccia. 



Fig. 144. Sporophyte of Sphaerocarpus texanus, X250. A, early stage, showing foot, 

 seta, and capsule with sporogenous tissue; B, spore mother cells and smaller, starch-filled 

 nutritive cells. 



3. Jungermanniales 



The Jungermanniales are by far the largest order of Hepaticae, embrac- 

 ing 150 genera and approximately 5,500 species. They are most abun- 

 dant in tropical regions, where they grow on the ground, on decaying logs, 

 and as epiphytes on the stems and leaves of trees. They require abun- 

 dant moisture and good drainage. Although much less numerous than 

 in the tropics, the group is well represented in temperate regions also. 

 The Jungermanniales comprise two great series, the Anacrogynae and the 

 Acrogynae. These will be considered separately. 



1. Anacrogynae 



In the "anacrogynous" Jungermanniales all the archegonia originate 

 behind the apical cell, none ever arising from the apical cell itself (Fig. 

 145yl). Thus the archegonia and sporophytes are always dorsal. Most 



