XXXVl] CYCADEOIDEA 403 



the seed-stalks are axial structures, institutes a comparison 

 between Welwitschia and Bennettites and regards each flower of 

 Welwitschia as a much reduced Bennettitean strobilus. Lignier 

 believes the interseminal scales to be leaves borne on the swollen 

 apex (receptacle) of an axis of the second order, while the seed- 

 stalks are fertile leaves of a unif oliar bud of the third order possibly 

 axillary though not necessarily so to the interseminal scales. My 

 own view, influenced by the examination of the immature flower 

 of Williamsonia scotica, is that the seed-stalks (megasporophylls) 

 and scales are homologous, the former being sporophylls and the 

 latter sterile foUage leaves, the whole flower, as Wettstein^ says, 

 consisting of a conical axis bearing numerous fertile and sterile 

 carpels enclosed by a perianth of bracts. WorsdelP, who shares 

 Celakovsky's opinion that sporophylls were originally radially 

 symmetrical organs bearing a terminal sporangium, regards the 

 flowers of Cycadeoidea Gibsoniana and other species as more 

 primitive than those of recent Cycads : he does not see any justi- 

 fication for the view that the Bennettitalean flowers are in advance 

 of those of existing Cycadean plants as regards a supposed tendency 

 towards the Angiospermous type. He maintains that Bennettites 

 'shows absolutely no indication of such an advanced structure ia 

 its essential organs, the sporophylls, which remain primitively 

 radial in structure, bearing the ovules in a terminal position.' 



Cycadeoidea dacotensis (McBride). 



McBride^ first described this Lower Cretaceous species from 

 the Black Hills of South Dakota as Bennettites dacotensis, the 

 generic name Cycadeoidea being adopted by Ward* who dis- 

 tinguished some of McBride's specimens as Cycadeoidea McBridei. 

 The stem is elUptical in section, 32 cm. long and 45 cm. in girth : 

 owing to the partial decay of the petiole-bases the ramental 

 reticulum forms a prominent feature. Numerous flowers, all of 

 which are approximately at the same stage of development, 

 project hke conical buttons above the general level of the stem- 

 surface^. The bisporangiate flowers consist of a conical receptacle 

 bearing interseminal scales and megasporophylls, the whole being 



1 Wettstein (11) p. 388. " Worsdell (00^). 



s McBride (93). * Ward (98) p. 205. 



5 Wieland (06) p. 185. See Wieland's description for further details. 



26—2 



