BRYOPHYTA 185 



other simple forms the antheridia are borne on unmodified shoots, but in 

 Porella and most members of the group they occur on special, short, lat- 

 eral branches. The antheridia are globular and mostly long-stalked, 

 developing as in the Anacrogynae except that the wall usually becomes 

 several layers of cells in thickness (Fig. 151Z)). 



The archegonia are generally borne on short lateral branches and are 

 always terminal. They occur singly or in a small group. They are com- 

 monly intermixed with paraphyses, usually surrounded by a perianth and 



Fig. 152. Longitudinal section of sporophyte of Porella, showing capsule with spore 

 mother cells and young slaters, X40. 



often also by an involucre lying outside the perianth. Both of these 

 envelopes are formed of united leaves. The archegonia develop as in the 

 Anacrogynae. In Porella six to eight neck canal cells are formed (Fig. 



Sporophyte. The sporophyte of the acrogynous Jungermanniales is 

 similar to that of the anacrogynous forms in that the seta is considerably 



