XXV] STAUEOPTERIS 465 



leaf borne by a plant closely allied to Etapteris {Zygopteris). 

 The broad rachis bears crowded pinnae given off at a wide 

 angle; the small pinnules are rather deeply lobed or pin- 

 natifid (3—10 mm. long by 1-5— 3 mm. broad). The lamina 

 is traversed by irregularly lobed and occasionally anastomosing 

 veins. In the fertile pinnae the segments have no lamina but 

 bear bundles of pedicellate sporangia. 



It should be noticed that the sporangia described by 

 Renault and by other authors as those of Zygopteris (fig. 

 319, A — C) have not been found in organic continuity with 

 a frond showing a well-preserved vascular strand. It is, however, 

 certain that this characteristic annulate sporangium, borne on 

 branched and slender pedicels, was produced on fronds with 

 a much reduced lamina belonging to some species of the 

 Zygoptereae, Etapteris and probably also Ankyropteris. 



Stauropteris. 



This genus was instituted by Binney for petioles from the 

 Lower Coal-Measures of Oldham (Lancashire). 



Stauropteris oldhamia Binney' is characterised by a stele 

 (figs. 308, E— G; 310, C; 320; 321) composed of four groups 

 of xylem which Bertrand regards as homologous with the 

 antennae of Diplolabis, Ankyropteris, and Etapteris, the hori- 

 zontal cross-piece of these genera being absent in Stauropteris. 

 Williamson spoke of this species as " one of the most beautiful 

 and also one of the most perplexing of the plants of the Coal- 

 Measures " ; he discussed its possible affinity with both Lycopods 

 and ferns, deciding in favour of the latter groups In transverse 

 section the petiolar vascular axis is approximately square, the 

 xylem groups forming the ends of the diagonals ; the tracheal 

 groups are separated by phloem and the centre of the stele in 

 the primary rachis is also occupied by that tissue, which is 

 connected by four narrow strips with the external phloem. The 

 structure of the petiolar vascular axis is very clearly shown in 

 the drawing by Mrs Tansley reproduced in fig, 320. Proto- 



1 Binney (72); Williamson (74) A. p. 685. 

 = Williamson (74) A. p. 685. 



