456 BETiTlirETTITALES [CH. 



Cycadeoidea micromyela (p. 415), a Jurassic French species, but 

 the ramenta are in part multicellular lamellae and the presence 

 of transitional forms suggests a possible derivation of hairs from 

 scales both in fossil species and in recent Cycads. The mega- 

 sporophylls and interseminal scales are much shorter than in 

 Cycadeoidea Gihsoniana and other species in which the axis of the 

 cone forms a depressed receptacle (c/. fig. 521, A, C), but they 

 correspond closely with those of several American species. In 

 Cycadeoidea Gihsoniana and C. Morierei the distal ends of the 

 interseminal scales are much broader and their diameter greatly 

 exceeds that of the micropylar tubes, 2-8 mm. as compared 

 with 0-25 mm., whereas in Williamsonia scotica the scales are 

 0-23 mm. broad and the micropylar tubes 0-15 mm. The mummi- 

 fied micropylar tubes of W. pectin bear a striking resemblance in 

 form and in the papillose epidermal cells to those of the Scotch 

 species. 



There are two additional points suggested by the structure 

 of the fertile region, namely the possibility that the megasporo- 

 phylls are arrested rather than immature organs and, secondly, 

 the method of pollination. In regard to the first there would seem 

 to be no adequate reason for doubting the correctness of the view 

 that the sporophylls are potentially perfect ovules which were 

 petrified at a comparatively early stage in development. The 

 dense woolly covering investing the surface of the scales and 

 megasporophylls recalls an inflorescence of Aesculus hippocastanum 

 in its winter-fur and hardly suggests a collection of ovules accessible 

 to microspores. In all probability at a later stage the protecting 

 bracts with their felt of hairs would bend outwards leaving exposed 

 the receptive micropyles. 



MiCEOSPOEOPHYLLS. 



In view of the association of microsporophylls and ovulate 

 strobili in the flowers of Cycadeoidea described by Wieland, most 

 of which are bisexual, it is reasonable to expect a similar association 

 in the flowers of Williamsonia which agree closely in the essential 

 features of both micro- and mega-sporophylls with those of 

 Cycadeoidea. It is, therefore, surprising that in no single case 

 have the microsporophylls attributed to Williamsonia been found 



