108 STRUCTURAL BOTANY 



cannot say for certain at present which of the hetero- 

 sporous forms really comes nearest to the Phanerogams ; 

 probably none of those now living bear much 

 resemblance to the real transitional forms, which we 

 suppose must have existed at an enormously remote 

 period, represented by some of the oldest fossiliferous 

 strata. Selaginella serves as well as any other type, 

 to enable us to form an idea how Cryptogamic and 

 Phanerogamic modes of reproduction are related. 



In finishing our account of the Vascular Cryptogams, 

 we have also come to the last of our series of vascular 

 plants. So far, the same general system of anatomical 

 structure has prevailed all through ; henceforth we shall 

 leave it behind altogether, and find ourselves among 

 plants with a much simpler, or at least a totally different, 

 internal organisation. 



