434 BENNETTITALES [CH. 



concrescent with the pyramidal axis and were then prolonged 

 as a wide infundibuliform apparatus (Williamson's carpellary 

 disc). This organ was, however, easily detached, and the rim 

 seen at r in fig. 547, C, represents its narrow broken base. With 

 this view I am in general agreement; but while Lignier regards 

 the funnel-like appendage as sterile and considers that similar 

 organs, but with a large central cavity at the base of the funnel, 

 may have been microsporophyll-discs which were borne below 

 the ovulate strobilus in the position occupied by the micro- 

 sporophylls in Cycadeoidea (fig. 528) my inclination is to see in 

 the terminal appendage a whorl of concrescent microsporophylls. 

 This view lacks the support of demonstration. It is obvious 

 from Williamson's specimens and from others described by 

 Saporta, Nathorst, and Lignier that the receptacle of Williamsonia 

 gigas was not so simple in its termination as that of the flowers 

 of Cycadeoidea. In Cycadeoidea dacotensis Wieland showed that 

 the apex of the receptacle bore a tuft of long interseminal scales, 

 and it is readily conceivable that these apical appendages were 

 still further developed in some Williamsonia flowers to form a 

 whorl of concrescent leaves borne on the prolonged apex of the 

 axis. There is little doubt as to the homology of interseminal 

 scales and microsporophylls, and there is no difficulty in supposing 

 that while in some flowers the foliar organs assumed the form 

 of interseminal scales of unusual length, in other species they 

 became microsporophylls. 



It is noteworthy that the radiating ridges on the circular area 

 shown in fig. 547, A', agree in position and approximately at 

 least in number with those on the sides of the cupular disc of the 

 microsporophyll-verticil of Williamsonia whitbiensis 1 . Nathorst 

 describes a specimen seen in a private collection in which an 

 infundibuliform appendage appeared to be preserved in situ at 

 the apex of a flower of Williamsonia gigas (cf. fig. 548, at). 

 Thomas 2 , in his description of Williamsoniella, compares the 

 radial ridges on the apical sterile portion of a flower of Williamsonia 

 gigas to the ridges on his Williamsoniella which are formed by the 

 tips of infolded microsporophylls. 



1 Nathorst (11) PI. n. 2 Thomas (15 2 ). 



