588 STUDIES IN FOSSIL BOTANY 



palisade - layer, thickened near the base (Fig. 211); 

 this is lined by a layer of small, thin-walled cells, 

 which also form the inner walls of the loculi (Fig. 2 1 o). 

 In dehiscence the two rows of loculi appear to have 

 split apart, the synangium thus opening by two valves, 

 while the individual loculi dehisced by longitudinal slits 

 (Figs. 210 and 211). If this was the case, the resem- 

 blance to Marattia extended to the mode of dehiscence. 



The microspores or pollen-grains have been care- 

 fully examined by Dr. Wieland, but without finding 

 any decisive proof of the presence of antheridial cells. 

 In size the microspores are intermediate between those 

 of Cordaiteae and recent Cycads. 



As already mentioned, the variation in structure 

 among the flowers of the American Bennettiteae, so far 

 investigated, is unimportant ; neither do their flowers 

 differ essentially, as it appears, from those of such 

 European species as Bennettites Gibsonianns and B. 

 Morierei. The group, in fact, was morphologically a 

 narrow one, however rich in specific forms. The 

 smallest number of stamens observed was ten, in 

 Cycadeoidea Jenneyana. The discovery of the bisexual 

 flower of Cycadeiodea Paynei is of interest, because in the 

 form of the receptacle and other characters this species 

 agrees so closely with Bennettites Gibsonianus as to 

 leave no reasonable doubt that the flowers of the 

 British species were likewise bisexual, the absence of 

 stamens in the specimens observed being simply due- 

 to the maturity of the fruit at the time of fossilisation. 

 The same applies to Bennettites Morierei, and indeed 

 it is quite probable, though not yet demonstrated, 

 that all Bennettiteae had bisexual flowers. In many 



