CORDAITEAE 545 



that no pollen-tube was developed, but that the relatively 

 large antheridium at once produced a number of sper- 

 matozoids, for we are probably justified in regarding 

 the cellular body within the pollen-grain of Cordaites 

 as an antheridium, rather than as a vegetative prothallus. 

 In the absence of a pollen -tube, the spermatozoids 

 would have needed to be more numerous, for, having 

 a longer distance to cover by their own movements, 

 they would presumably have reached their goal with 

 less certainty. The pollen-tube may probably be re- 

 garded as a later adaptation, which served the purpose 

 of economising spermatozoids, and ultimately rendered 

 their motility unnecessary. Even in the Cycads and 

 Ginkgo, where the pollen - tube serves mainly as an 

 anchoring and food - absorbing organ, its growth ulti- 

 mately brings the spermatozoids with much precision 

 to their goal — the necks of the archegonia. 1 



As regards the morphology of the female Cordaian- 

 thus, there seems no reason to doubt M. Renault's view, 

 that the ovules were borne singly, on the apex of short 

 axillary shoots, as in Taxus. If we compared the 

 female catkin with a cone, such as that of the Abietineae 

 or Taxodieae among recent Conifers, we should be led 

 to adopt one of the theories which interpret the semi- 

 niferous scale in those families as representing a reduced 

 axillary shoot. Other authors have preferred the com- 

 parison with Gnetaceae, and especially with Ephedra, 

 chiefly on the ground of the double integument or 

 envelope of the ovule. It does not seem to be perfectly 

 certain, however, that this structure in Cordaites was 



1 See, for example, Webber, Spermatogenesis and Fecundation ofZamia, 

 U.S. Dept. of Agriculture, 1901, p. 63. 



