IV] PROCORMOPHYTA 49 



vascular connexion exists between the main axis and its 

 branches ? Surely here the evidence is emphatically on the side - 

 of primitiveness ? 



The morphological data appear to us to be equally emphatic. 

 In the first place the fructification is wholly Thallophytic. The 

 sporangia are quite unlike those of any fern borne on a highly 

 reduced frond, and they find their nearest homologues among 

 the Red Algae and those forms which possess a simple type of 

 carpogonium. We have further no evidence at all of more than 

 one type of reproductive organ, although the complete plant is 

 undoubtedly known. 



Further there is the evidence of the emergences, for such we 

 believe to be the real nature of the lateral organs on the erect 

 axes. These are anatomically non-vascular and histologically 

 emergences and not branches, as their anatomy clearly shows. 

 As we have pointed out here, these structures, in Psilophyton, 

 are of varied size, micro- or macroscopic, and in the latter case 

 scale-like. So far as we can see there are no grounds, either 

 anatomical or morphological, for regarding these structures as 

 leaves, however reduced. Yet this is the interpretation which 

 must be put upon them if these genera are to be regarded as 

 very reduced Pteridophytes. Finally the habit of Psilophyton, a 

 rhizome giving off rhizoids, and erect naked axes, some termi- 

 nating in sporangia, is much more typically Thallophytic than 

 Pteridophytic. 



We fail to find any ground of comparison except in habit 

 (which taken alone is a perfectly valueless character) to the 

 living plant Psilotum. The fructification and the vascular 

 structure of the two are quite distinct. Further if, as we believe, 

 Psilotum is rightly placed in close relation to Tmesipteris, it is 

 obvious that any affinity between these plants and Psilophyton 

 must be very remote. 



We thus regard Psilophyton as first and foremost a Thallophyte, 

 which, while still Thallophytic in habit, may occupy anatomically 

 a place half-way between the Thallophyta and Pteridophyta. 

 We propose to term such plants Procormophyta. 



With regard to the other genera of the Psilophyton flora, the 

 evidence is less emphatic, since they are less completely known. 



