GENERAL RESULTS 617 



It will be noticed that this grouping crosses the 

 customary division of Vasculares into Pteridophyta 

 and Spermophyta. Though the traditional classifica- 

 tion will, no doubt, continue to be used on grounds 

 of convenience, 1 it no longer, in the light of the 

 palseobotanical evidence, expresses a natural arrange- 

 ment, for the affinities between Pteridosperms and Ferns 

 appear to be far closer than those between Ferns and 

 any other Pteridophytic phylum. 



The divisional name Pteropsida is taken from 

 Professor Jeffrey, and used in the same sense as by him. 

 His Lycopsida, however, are here limited to the 

 Lycopodiales, the typically microphyllous phylum, 

 while he included our Sphenopsida in the same 

 division. This is not the place for a detailed discussion, 

 but I am no longer of opinion that the affinity between 

 Lycopods and the sporangiophoric Pteridophytes (Pro- 

 fessor Bower's name for our Sphenopsida 2 ) is sufficiently 

 established to render their inclusion under a common 

 name expedient. The name Sphenopsida has been 

 selected because of the synthetic character of the class 

 Sphenophyllales, rendering them the best type of the 

 division. 



A certain degree of convergence between the main 

 divisions of Vascular Plants may be traced as we 

 follow their history back to its earliest records. 

 Some of the oldest Sphenopsida show an approach 

 in leaf-characters to the megaphyllous Fern-phylum, 

 while anatomically they tend rather towards the 



1 As in the subtitles given to the two volumes of the present book. 



2 F. O. Bower, Origin of a Land Flora, 1908, Chapters xxvii.-xxix. 

 The author's association of the classes with specialised sporangiophores 

 appears eminently natural and suggested the arrangement here adopted. 



