SUBGENEEA AND SPECIES OF SELAG-INELLA. 155 



It may be said that I am attempting to found a 

 taxonomy on as narrow a basis as the most rigid upholder 

 of external features as diagnostic of species and subgenera. 

 In answer to that I may reply that I do not propose to 

 base a revised classification on anatomical characters 

 exclusively ; but it seems to me in the first place that 

 anatomical characters cannot be omitted from consider- 

 ation, as has been done in the past in this family, more 

 especially when we take into account how varied and 

 important these anatomical characters are. 



The question at once arises to which, external mor- 

 phology or internal anatomy, must we give the most 

 weight ? It will surely be admitted that in constructing a 

 phylogeny of the group more weight must be given to the 

 internal than to the external structure, since the former 

 is less liable to external influences during the process of 

 evolution. Even extreme differences in morphology and 

 habit have not been considered of sufficient importance to 

 separate species of other genera which agree fundamentally 

 in anatomical characters ; why should the method adopted 

 in the Selaginellacege be different from that in others cases ? 



