52 PTERIDOSPERMEAE [GEL 



remains of a stellate group of cupular segments. An examination 

 of the specimen in Dublin convinced me that there is no satis- 

 factory evidence of the seed-nature of the appearance on the 

 rock believed by Johnson to be an elliptical Lagenostoma-like 

 seed. The actual attachment of the stellate lobes to the pinnae of 

 the frond is not clearly demonstrated. 



iii. Microsporangia. 



In 1905 Kidston 1 announced the discovery of microsporangia 

 on fronds of Lyginopteris : he described specimens from the Coal 

 Measures of Dudley identified by him with Sphenopteris Hoening- 

 hausi showing sterile and fertile pinnae in organic connexion. 

 The fertile pinnules (fig. 407, B) are slightly expanded distally 

 into an oval limb about 2 mm. long bearing 6 to 7 bilocular 

 fusiform microsporangia 3mm. long and 1-5 mm. broad: in the 

 immature condition the sorus is hemispherical, the summit being 

 formed of the incurved apices of the sporangia. At maturity 

 the sporangia spread out, the sorus assuming the form of an 

 epaulet. Fig. 408, H, shows a sorus in transverse section and in 

 fig. 408, G, the limb and two pendulous sporangia are shown. 

 The microspores, 50 70 ^ in diameter, are studded with numerous 

 blunt spines and each spore shows a triradiate ridge. The section 

 reproduced in fig. 407, A, from the Coal Measures of Oldham is 

 probably a bilocular sporangium of the same type as those 

 described by Kidston from Dudley. Dr Kidston 2 describes a 

 second type of microsporangial sorus as Crossotheca Hughesiana 

 which agrees closely with C. Hoeninghausi, but the fertile segments 

 are not associated with any sterile pinnae. The generic name 

 Crossotheca, founded by Zeiller 3 in 1883, was substituted for 

 Sphenopteris on the ground that Brongniart's species S. Hoening- 

 hausi is shown to possess sporangia of the Crossotheca type. If 

 Kidston's specific determination is correct, his discovery demon- 

 strates that Lyginopteris fronds bore microsporangia having the 

 characters of Crossotheca, a type characteristic of several Carboni- 

 ferous species belonging both to the form-genera Sphenopteris 

 and Pecopteris. Keference has already been made to the difficulty 

 of distinguishing between impressions of fronds of the Sphenopteris 



1 Kidston (05). 2 Kidston (06) B. 3 Zeiller (83) B. 



