436 



BBNNETTITALES 



[CH. 



Some reniform synangia (fig. 549, B) occur in the rock just above 

 the cup. The sporophylls spread outwards from the base and 

 then curve inwards, bending outwards again as they become 

 free. A portion of a microsporophyll is shown in fig. 550 bearing 

 segments projecting inwards as 

 in W. sfectabilis (fig. 551). This 

 specimen, which occurs in as- 

 sociation with female flowers, is 

 regarded by Mr Thomas as part 

 of a unisexual flower. He discusses 

 the possibihty of its connexion 

 with an ovulate receptacle and 

 expresses the opinion that if it 

 were borne at the upper end of 

 a bisporangiate flower the whole 

 would be top-heavy and the 

 arrangement uneconomical. On 

 the other hand if, as suggested 

 on page 434, the flowers were 

 bisexual the staminate disc, which 

 reached maturity before the ovules, 

 may have been thrown off, as in 

 Cycadeoidea, before the seeds were 

 ripe. The form of the disc resembles that of the Indian 

 specimen described on another page as Williamsonia sp., cf. 

 W. setosa Nath. ; it does not, I venture to think, afford an 

 argument against the view that the microsporophyll-cup of some 

 Williamsonia flowers was attached near the apex of the receptacle 

 and was formed of modified foliar organs homologous with those 

 which, in the ovulate portion of the flower, constitute the inter- 

 seminal scales and megasporophylls. 



A further consideration of the microsporophylls of Williamsonia 

 will be found in a later section of this chapter. 



Williamsonia spectabilis Nathorst. 



This species^, the first example of undoubted microspore- 

 bearing organs referred to Williamsonia, was founded on material 



Fig. 550. Williamsonia gigas. Side- 

 view of an incomplete staminate disc 

 showing the basal cup torn at the 

 lower end and part of one of the free 

 microsporophylls. (Diagrammatic 

 drawing, after Thomas; nat. size.) 



1 Nathorst (09) p. 6, Pis. jl., n; (11) p. 5, Pis. i., m; (12). 



