470 



BENNBTTITAIiES 



[CH. 



Fig. 572. Williamsoniella 

 coronata. Apical disc with 

 megasporophylls and in- 

 terseminal scales at the 

 base. (After Thomas ; 

 X 3.) 



flower. Tte corona is surraounted by a small conical elevation 

 wtich represents the apex of the fertile axis. An apical view 

 of an unexpanded flower is shown in fig. 571, B; the tips of 12 

 sporophylls are closely pressed against the corona which probably 

 consists in part at least of fused inter- 

 seminal scales. The microsporophylls 

 were shed after the dehiscence of the 

 synangia. Bach sporophyll is flattened 

 on the sides and thicker on the curved 

 outer edge ; the synangia, usually in two 

 rows of three, are borne on the sloping 

 sides (figs. 569, 570). The surface of a micro- 

 sporophyll is covered with small rounded 

 projections which produce a characteristic 

 appearance. The form of a microsporophyll 

 in section is shown in fig. 570 : the synangia 

 are similar in shape to those of Cycadeoidea 

 and Williamsonia {cf. figs. 531, 549, etc.) but there are no external 

 indications of septa like those seen in some other types. On 

 macerating some specimens it was found that the spores occur 

 in about 20 groups. The circular or elliptical spores are 0-02 mm. 

 in diameter. The walls of the epidermal cells of the micro- 

 sporophylls are straight: the stomata, which show the features 

 characteristic of the Bennettitales, agree closely with those of 

 Taenopteris vittata. 



The interseminal scales associated with the ovules and covering 

 the pyriform axis above the microsporophylls are more or less 

 flattened and hexagonal and the micropylar tubes often project 

 far beyond the scales. Each micropyle-tube is surrounded by 

 5 — 6 interseminal scales {cf. fig. 564). The ovules differ from 

 those of Cycadeoidea Gibsoniana in the absence of a distinct 

 pedicel and agree with the corresponding organs of Williamsonia 

 scotica^ In the absence of epidermal papillae the micropylar 

 tubes resemble those of Wielandiella angustifolia. As already 

 stated, the flowers appear to be without protective bracts, but in 

 the shale from which the specimens were obtained a few bract-like 

 organs were discovered consisting of a lanceolate lamina 1-5 cm. 



^ See page 449. 



