642 STUDIES IN FOSSIL BOTANY 



Though the Botryopterideae formed the basis of the 

 group Primofilices, as proposed by Mr. Arber, some doubt 

 has since been expressed whether this family really 

 belonged to the Primofilices in the true sense of the 

 word. 1 Miss Stopes points out that, since many of the 

 Botryopterideae have tracheae with multiseriate bordered 

 pits, like those of Gymnosperms, they are in this respect 

 not absolutely true Ferns, but have taken one step 

 towards Gymnosperm anatomy ; the group therefore 

 appears to contain members which are " Pro-Pterido- 

 sperms " rather than Primofilices pure and simple. 

 The view has been taken here (p. 345) that the 

 Botryopterideae are probably an offshoot from the same 

 line of descent with the later Ferns, rather than their 

 direct ancestors. They seem, however, to have been 

 sufficiently near the original stock 2 to deserve in an 

 eminent degree the name Primofilices, which does not 

 necessarily imply direct ancestry. As regards the 

 pitted tracheae, it appears probable that this form of 

 water-conducting element was once common to the 

 Fern phylum generally, but that the true Ferns have 

 since for the most part lost it, adopting the very 

 specialised scalariform type of vessel which is now 

 characteristic of them (p. 3 1 4). 



The question of the affinity of the Botryopterideae 

 to the Pteridosperms is of great interest. The Pterido- 



1 M. C. Stopes, "A New Fern from the Coal- Measures, Tubicaulis 

 Sutcliffii," Mem. and Proc. Manchester Lit. and Phil. Soc. vol. 1. No. IO, 

 1906, p. 23. 



2 See especially the fine series of memoirs by liidston and Gwynne- 

 Vaughan on the fossil Osmundaceae, in which the close relations of this family 

 with the Botryopterideae are demonstrated, Trans. Royal Soc. Edi?ihtrgk, 

 vol. xlv. Part iii. p. 759, 1907 ; vol. xlvi. Part ii. p. 213, 1908 ; Part iii. 

 p. 65, 1909. 



