382 BENNETTITALES [CH. 



The structure of the flowers is one of the most obvious differ- 

 ences between Cycadeoidea and recent Cycads (cf. figs. 393, 394). 

 The bisexual flowers of the fossil stems are comparatively small, 

 not exceeding a few centimetres in length, like a hen's egg or 

 a medium-sized pear and in marked contrast to the male and 

 female cones of modern Cycads (cf. figs. 393, 394). A verticil of 

 pinnate microsporophylls is attached by a circular collar formed 

 of the concrescent bases of the sporophylls to the lower portion 

 of the receptacle; each pinnule bears several shortly-stalked 

 synangia divided into loculi containing microspores usually with 

 smooth walls and similar, except in their larger size, to those of 

 modern Cycads (fig. 532). Sections of some microspores figured 

 by Wieland 1 show what appear to be cells in the spore-cavity, 

 but they are larger than ordinary prothallial cells and their true 

 nature is doubtful. We lack information both as regards the 

 nature of the male gametes and the tissue formed on the germina- 

 tion of the spores. The free portions of the microsporophyll- 

 whorl may consist of as many as 20 pinnate sporophylls, but the 

 number is generally smaller; these are much longer than the 

 ovulate part of the flower and in an immature state the ends of 

 the sporophylls are bent inwards and downwards (fig. 513) between 

 the bracts and the receptacle. After expanding and shedding 

 the spores the whole male disc is thrown off leaving a narrow rim 

 below the hemispherical or conical receptacle (fig. 514, d). The 

 sterile distal end of a microsporophyll is generally slightly expanded 

 and spathulate; in C. colossalis 2 it bears a pair of wing-like 

 appendages (fig. 533). 



The upper part of the receptacle is covered with two kinds of 

 organs which together form a layer of uniform depth; these are 

 believed to be homologous, foliar structures ; the majority are sterile 

 and have the form of slender long and narrow appendages (fig. 514) 

 each normally with a single axial vascular strand. These so-called 

 interseminal scales increase in breadth in the apical region and form 

 polygonal summits less than a millimetre in breadth or exceeding 

 2 mm. The low pyramidal apices of the interseminal scales give 

 a mosaic-like appearance to the surface of the ovulate receptacle 

 (fig. 515). In the lower part of the receptacle these sterile 

 1 Wieland (06) p. 160, fig. 84. 2 Ibid. (14). 



