412 SPHENOPHYLLUM. [CH. 



European species. A specimen of Sphenophyllum oblongifolium, 

 which Prof. Zeiller showed me in illustration of this point, was 

 practically indistinguishable from Ti'izygia^. 



In some of the earlier descriptions of the Indian species the 

 generic name Sphenophyllum^ was used by McClelland and 

 others, but the supposed difference in the leaf-whorls was made 

 the ground of reverting to the distinct generic term Trizygia. 

 Now that a similar type of leaf-whorl is known to occur in 

 Sphenophyllum, it is better to adopt that genus rather than to 

 allow the question of locality to unduly influence the choice 

 of a separate generic name for an Indian plant. 



III. Affinities^ range and habit of Sphenophyllum. 



It has been pointed out in the description of Sphenophyllum, 

 that the most widely separated families of recent plants have been 

 selected by different authors as the nearest living allies of this 

 Palaeozoic genus. It is now generally admitted that Spheno- 

 phyllum is a generic type apart ; it cannot be classed in any 

 family or subclass of recent or fossil plants, without considerably 

 extending or modifying the recognised characteristics of ex- 

 isting divisions of the plant-kingdom. The anatomical charac- 

 ters of the Sphenophyllum stem are such as one finds in some 

 recent genera of the Lycopodinae, especially Psilotum. If the 

 stele of Psilotum were composed internally of a solid strand of 

 xylem, we should have a close correspondence between the 

 centripetally-developed wood of this genus and that of 

 Sphenophyllum. Similar comparisons might be drawn with 

 other existing genera, but the more detailed consideration of 

 the affinities of the Palaeozoic plant will be more easily dealt 

 with after other members of the Pteridophytes have been 

 described. The recent discovery of an entirely new type of Car- 

 boniferous strobilus in rocks of Calciferous sandstone age on the 

 shores of the Firth of Forth has thrown new light on the 

 position of Sphenophyllum. Cheirostrohus Pettycurensis, the 

 new cone which Scott has described in an able memoir, affords 



1 Vide also Zeiller (922), p_ 75, 2 Feistmantel (81), p. 69. 



