FOSSIL GYMNOSPERMS 139 



suggests a condition which needs further material before it can 

 be homologized with any of them. 



The pollen grains are remarkably well preserved, the exine 

 being cuticularized and covered with a fine " shagreenlike " 

 reticulation. As these spores have been found both in the spo- 

 rangia and in the pollen chamber, there can be no doubt as to 

 their relation to the ovules examined. The most remarkable 

 feature of the group is the presence of a distinct tissue within 

 the pollen grain while still in the sporangium. This tissue con- 

 sists of a group of small polygonal cells against the wall on one 

 side (Fig. 95, C). After pollination, while in the pollen cham- 

 ber, the spore is said to increase very much in size, and the inter- 

 nal tissue develops still further. If these statements can be re- 

 lied upon, the male gametophyte of Cordaitales is one of extraor- 

 dinary interest, for it is far more primitive in character than that 

 of any other known Gymnosperm, and points to the earliest stages 

 of heterospory, earlier than in any existing heterosporous Pteri- 

 dophyte. Whether the cells of this internal tissue are vegetative 

 or sperm-producing is a matter of conjecture. In any event, 

 the reduction of the male gametophyte is very much less than in 

 any other known Seed-plant. Taken in connection with the pres- 

 ence of ciliated male cells in the Cycads and Ginkgo, and of a 

 very deep pollen chamber which eventually deepens down to the 

 embryo sac, it might be inferred that in Cordaitales there was 

 little if any development of a pollen tube, and that swimming 

 male cells, if not actually sperms, were discharged within easy 

 reach of the archegonia. It must be remembered that in 

 the Cycads and Ginkgo the pollen tube does not serve the pur- 

 pose of a sperm carrier, and there is no reason to suppose that 

 there was any such method of sperm transfer in the Cor- 

 daitales. In case the internal tissue of the pollen grain is 

 antheridial, it would indicate the production of more numer- 

 ous male cells than in any other Seed-plant. The whole struc- 

 ture is so suggestive of a theoretical transition stage between 

 Pteridophytes and Spermatophytes that it is a temptation to 

 make more out of it than the amount of observed material may 

 justify. 



The ovules occur in strobili similar to those which bear the 

 stamens, but the bracts are longer and more overlapping, and a 

 terminal tuft of long bracts crowns the strobilus. The solitary 



