130 



MEDULLOSEAE 



[CH. 



in which they agree closely with the spores of Dolerofhyllum 

 fertile described by Renault^, In both cases the spores tend to 

 be arranged in long groups and they are practically identical 

 in form and in the nature of the exine; those of Dolerophyllum 

 are 280/x long while those of W. fertilis reach a length of 220yn. 

 In some of _ the Whittleseya spores the exine has split as in the 

 specimen shown in fig. 429, but in others there are two curved 

 lines along which dehiscence has begun, a character in which 

 the spores appear to be identical with those of Dolerophyllum 



A B 



Fig. 429. Microspores of Whittleseya elegans. A, a group of spores ; B, a 



spore. (Preparations made from an American specimen, No. 2314, in 

 Dr Kidston's Collection.) 



described by Renault who speaks of dehiscence by means of an 

 operculum. There is, I venture to think, Uttle doubt as to the 

 very close affinity of the two types. The systematic position 

 of Dolerophyllum is not certainly established; if the generic 

 identity of the leaves described as D. Berthieri Ren. and the 

 petrified specimens named D. fertile is assumed, it is a legitimate 

 inference that the genus is founded on fertile pinnules of a Pterido- 

 sperm with foliage of the Neuropteris or Cyclopteris form. It 

 would seem probable that both Whittleseya and Dolerophyllum 



1 Renault (93) A. PI. Lxxii; (96) A. p. 268. See page 137. 



