2o6 Alexander W . Evans, 



phyte and gametophyte have several important features in common. 

 In the Anthoceros sporophyte a definite photosynthetic tissue is 

 present in the wall of the capsule, and the interior is occupied by 

 a well-developed columella. From a sporophyte of this general 

 character the sporophytes of the Jungermanniales and Marchanti- 

 ales have presumably been derived by a process of degeneration or 

 simplification, the photosynthetic tissue disappearing entirely and 

 the columella either persisting in the form of an elaterophore or 

 becoming completely lost. The final stage in the process is seen 

 in the sporophyte of Riccia, which consists of a simple spherical 

 spore-case, enclosed by a delicate and ephemeral wall. 



According to another view, which is perhaps more prevalent, the 

 Riccia type of sporophyte is to be regarded as primitive. From 

 this type, by a process of sterilization and specialization, the more 

 complex types of sporophyte have been derived, culminating in the 

 most complex type of all found in the Anthocerotales. Whichever 

 view is accepted it is clear that the sporophyte of Riccardia with 

 its well-developed elaterophore, occupies an intermediate position 

 in the series. It is apparent, therefore, that this sporophyte can 

 not be regarded as a primitive structure, whatever views are held 

 regarding the gametophyte. 



