212 D- H. Scott. 



have a iniique fonn of seed-investment. The characters of the male 

 fructification, if we maj' take Crossotheca as a fair example, appear 

 to have been frankh' Cryptogamic, and the same applies to the ana- 

 tomy of such plants as Sutdifßa and Heterangmm, genera which show 

 such evident relations to MeduUosa and Lijginodendron respectively, 

 that we cannot doubt their being Pteridosperms. It seems to me 

 desirable to give full weight to primitive characters such as these, 

 and to keep the Pteridosperms distinct, rather than to merge them in 

 the Gymnosperms, a group which has departed so much further from 

 Cryptogamic traditions. At the same time I fully recognise that this is 

 a matter of expediency rather than of principle, for further research 

 will undoubtedlj' tend to fill up the gap between the two classes. 



A more fundamental question is that of the relation of the Pterido- 

 spermeae to the Cryptogams. As has been sufficiently shown in the 

 preceding pages, all the characters in which the Pteridosperms show 

 Cryptogamic affinities, whether in anatomical structure, in the morpho- 

 logy of the sporophyll, or in the nature of the male fructification, 

 point clearly to their derivation from ancestors belonging to a Fili- 

 cinean stock. They have been described as ''Ferns which have be- 

 come Spermophytes", and the phrase is appropriate. When, however, 

 we come to inquire into the characters of the Filicinean group from 

 which the Pteridosperms arose, we find that our data are insufficient. 

 They are themselves, in all probability, as ancient as any land-plants 

 known to us, and their actual origin lies further back than our re- 

 cords at present extend. Considering that some of the Pteridosperms 

 show a decidedlj^ simple anatomical structure (as in Heterangium) we 

 may assume that they were derived from plants of a simple type of 

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

 known "Primofilices" with the ancestors of the Pteridosperms; they 

 are not nearly old enough geologically, and our knowledge is much 

 too narrow to enable us to determine how far they may have re- 

 tained the characters of the original common stock. The utmost we 

 can venture to say is, that these simpler Palaeozoic Ferns, the Botryo- 

 pterideae and their allies, probably stand nearer the Cryptogamic 

 progenitors ot 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 31edi(Uosa, 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. 



