678 



PTERIDOSPERMS, ETC. 



[CH. 



but no fertile British specimens are recorded. Stur places this 

 species in the genus Scolecopteris, and Potonie regards the 

 sporangia found by him on Permian fronds, which may be 

 identical with Pecopteris arborescens, as conforming to those of 

 the Asterotheca type. It is impossible to decide on the evi- 

 dence available whether this species is a Pteridosperm or a 

 fern, but there is a natural inclination in doubtful cases to give 

 preference to the first of these two choices. 





ru 



i.-'A'iii, 





i/s 





-4.1. 



:il^J 





M 



Fig. 376. Pecopteris arborescens (Schloth.). From the Upper Coal-Measures of 

 Badstock. From a photograph by Dr Kidston. Reduced. 



The numerous fronds from Carboniferous and Permian rocks 

 described as species of Pecopteris exhibit a considerable range 

 of variation in the form of the pinnules. In many species the 

 pinnules are of the type represented in fig. 352, D ; in others 

 the lamina of the ultimate segments is slightly contracted at 

 the base and the secondary veins are given off at a more acute 



