XXXVn] WILLIAMSONIA 457 



in actual connexion with a receptacle bearing interseminal scales 

 and megasporophylls. The same statement holds good with 

 regard to the Williamsonias discovered in Mexico. Nathorst 

 believes that the microsporophylls on which he has founded several 

 species are unisexual flowers with the possible exception of W. 

 pyramidalis^ This species, found by Dr Halle at Cloughton Wyke, 

 is represented by a small ovulate strobilus characterised by a 

 conical receptacle with a blunt mucronate apex : with it is asso- 

 ciated a microsporophyll bearing synangia. The orientation of 

 the two specimens is such as to suggest an original connexion. 

 As Nathorst says, there is, however, no proof that the two belong 

 to one flower. Wieland^, though believing that the existence 

 of bisporangiate Williamsonia flowers is 'reasonably certain,' 

 agrees with Nathorst's conclusion as to the unisexual character 

 of W. spectabilis and W. pecten. On the other hand, he regards 

 the microsporophyll- verticil which was first described by William- 

 son as a carpellary disc, then named by Nathorst^ W. bituberculata 

 and afterwards identified as a microsporophyll-disc closely allied 

 to W. whitbiensis, as the staminate part of W. gigas. This view 

 is, in my opinion, impossible to reconcile with the nature of the 

 specimen. If, as Wi eland suggests, it is the staminal collar split 

 off from the base of a large ovulate cone like that of Williamsonia 

 gigas, one would expect to find a central space in the middle of 

 the cupular base large enough to embrace the receptacle. Neither 

 in this specimen nor in several other forms of microsporophyll- 

 verticils is there such a central space. It is clear that the discs 

 described as W. spectabilis, W. whitbiensis, and other species 

 were not borne as concrescent collars on a stout axis as are the 

 corresponding organs in Cycadeoidea. The Indian specimen 

 reproduced in fig. 557 and the very closely alHed type W. setosa 

 are incomplete at the centre and may possibly have been borne 

 at the base of an ovulate bisporangiate strobilus, but there is 

 no definite evidence that this was the case. Moreover, in W. 

 spectabilis the lower part of the cup (fig. 551) easily splits away 

 from the rest of the staminate disc, and- this may explain the 

 central space in the specimen shown in fig. 549, A. liW . spectabilis, 



' Nathorst (11) p. 24, PI. v. figs. 9—11. " Wieland (11) p. 462. 



• Nathorst (09) p. 10; (11) p. 14. 



