CH. XXXl] 



PECOPTERIS PLUCKENETI 



167 



(figs. 225 and 226, vol. n.). The variation in the form of the 

 pinnules is shown in fig. 442, A, which represents both the apical 

 portion and parts of pinnae 10 cm. lower on the rachis of a large 

 leaf from the Coal Measures of Radstock. The species is character- 

 istic of the Upper Coal Measures and is recorded also from Permian 

 strata. In 1883 Sterzel adopted for this species the generic 

 name DicJcsonites because of the occurrence of shallow circular 

 cups at the end of the lowest lateral vein on some of the pinnules 

 which he believed to be sori of the Cyatheaceous type. The cups 



A 



FIG. 442. Peco2>teris Pluckeneti. A, apex and lower pinnae (Kidston Coll., 

 234); B, pinnule with supposed sorus (after Sterzel); C, pinnule with seeds 

 (after Zeiller). 



have an involute margin and occasionally a small scar in the centre 

 (fig. 442, B). Stur 1 declined to accept Sterzel's evidence as 

 satisfactory and suggested a fungal origin for the sorus-like 

 impressions, a view, as Sterzel objected, that is rendered improbable 

 by the constant position of the single cups on several pinnules. 

 The nature of Sterzel's 'sori' has not been demonstrated: it is 

 suggested by Grand' Eury 2 that they mark the position of micro- 



1 Stur (85) B. p. 293. 2 Grand'Eury (05). 



