454 BENNETTITALES [CH. 



a striking feature of the cuticular membrane of Ptilophyllum 

 leaflets 1 . 



In the examination of the type-specimen the first section cut 

 was transverse to the axis (fig. 562), and this happened to traverse 

 the lowest part of the fertile region of the receptacle, as was shown 

 by the fact that in the next lower section the axis bore only 

 bracts and hairs. It is clear that the sterile portion of the recep- 

 tacle passed abruptly upwards into the fertile region, and it is 

 extremely unlikely that any microsporophylls were borne at the 

 base of that portion of the cone-axis which produced the scales 

 and megasporophylls. The cone was, in all probability, uni- 

 sexual. On the analogy of the cones shown in figs. 513, 514, one 

 would expect to find between the sterile and fertile regions either 

 a verticil of microsporophylls or the remains of an annular disc 

 from which the effete sporophylls had been detached. There is 

 no trace of any such disc, and the fact of the immaturity of the 

 megasporophylls renders it unlikely that were the cone bisexual 

 the microsporophylls would have been detached. As previous 

 records show, there is nothing improbable in the occurrence of a 

 unisexual Bennettitean flower. These remarks are made in view of 

 an opinion expressed by Dr Wieland that the bracts with lateral 

 appendages (fig. 561, I), to which allusion has been made, are 

 microsporophylls and that if the cone had been sliced longitudinally 

 the presence of a microsporophyll-disc would have been discovered. 

 The latter possibility has already been considered, and as regards 

 the former there is nothing in the structure of the small lateral 

 appendages of the longest bracts to indicate that they were con- 

 nected with spore-production. It is not unlikely that the bracts 

 with small outgrowths (fig. 561, I) correspond to the more leaf- 

 like bracts of Wielandiella and Williamsoniella. The two sets of 

 organs spoken of as interseminal scales and megasporophylls 

 are probably homologous, foliar, structures ; in the one case leaves 

 transformed into cylindrical organs bearing terminal integument ed 

 and undifferentiated megasporangia and, in the other, sterile 

 or sterilised sporophylls. The polygonal truncate distal end of 

 an interseminal scale is flat or slightly concave and covered by 



1 Thomas and Bancroft (13) p. 184. 



