THE GYMNOSPERMAE : CYCADALES, ETC. 725 



central bundle ends in a tassel of branches below the nucellus. The bundles 

 outside the stony layer do not branch but pass upwards through the outer 

 flesh to the micropyle. This structure should be compared with that described 



POLLEN CHAMBER 

 NUCELLUS 



MICROPYLE 



STONY LAYER 



NNER FLESH 



PROTHALLUS 



FLESH 



B 



D 



F 



Fig. 730. — Cycos reroluta. Structure of the seed. A, Longitudinal section of the 

 seed with vascular bundles shown in black. B to F, Vascular supply to the seed 

 as seen in a series of transverse sections of the pedicel, in succession from below 

 upwards. F is through the base of the seed. {After Slopes.) 



under Taxiis, where the correspondence with some of the fossil seeds is 

 pointed out. The existence of this concentric structure in the seed pedicel 

 is of great interest as a link with the fossil Bennettitales, in which the seed 

 pedicel contains a single concentric strand which passes upwards into a circular 

 zone of transfusion tissue surrounding the ovule. 



The early development of the ovule has not been fully studied in Cycas, 

 and we can only state what has been found in related genera. At an early 



