THE PTERIDOSPERMS AND THE SEED 253 



probability, as ancient as any land plants known to us, 

 and their actual origin lies further back than our records 

 at present extend. Considering that some of the Pterido- 

 sperms show a decidedly simple anatomical structure 

 (as in Heterangium) we may assume that they were 

 derived from plants of a simple type of organisation. 

 It would be rash in the extreme to identify any of the 

 known ' Primofilices ' with the ancestors of the Pterido- 

 sperms ; they are not nearly old enough geologically, 

 and our knowledge is much too narrow to enable us to 

 determine how far they may have retained the characters 

 of the original common stock. The utmost we can 

 venture to say is, that these simpler Palaeozoic Ferns, 

 the Botryopterideae and their allies, probably stand 

 nearer the Cryptogamic progenitors of the Seed-plants 

 than any other group of which the record has come 

 down to us. 



" Where we find among the Pteridosperms characters 

 resembling those of more advanced Filicinean types, 

 they are probably to be attributed to parallel development 

 rather than to inheritance. The ' polystely ' of Medullosa, 

 for example, if, as there is reason to believe, it arose 

 within the Pteridospermic family Medulloseae, was not 

 a directly inherited Filicinean character, but rather a 

 new development on Filicinean lines. 



" We may sum up the position of the question as to 

 the derivation of the Pteridosperms in the statement 

 that all the evidence points to their having sprung from 

 the same stock with the Ferns. The antiquity of the 

 Ferns, and especially of the comparatively simple types 

 represented by the Botryopterideae and related forms, 

 appears sufficiently established to afford an historical 

 basis for this conclusion." 



BENNETTITES AND THE PRIMITIVE FLOWER 



While progress had thus been made not only in tracing 

 back the origin of the seed habit but also in reconstructing 



