CORDAITALES 



179 



nitely referred as yet to either Cordaitales or Cycadofilicales, similar 

 groups of internal cells have been found, as in Stephana spermum 

 (p. 50), indicating that the male gametophyte among paleozoic seed 

 plants must have been more primitive in structure, in the amount of 

 either prothallial or spermatogenous tissue or both, than in living 

 seed plants. It is interesting to note, in this connection, that an 

 excess of male prothallial tissue, as compared with the other living 

 gymnosperms, has been found among the podocarps and araucarians. 



ap 



Fig. 210. — Cycadinocarpus angustodunensis: longitudinal section of upper part 

 of ovule; mi, micropyle; int, integument; pc, pollen chamber with pollen grains; nu, 

 nuceUus; ar, archegonia; fr, female gametophyte. — After Renault (2). 



In some of the sections of the seeds of Cordaitales, the mature 

 embryo sac, containing the female gametophyte (endosperm) with its 

 - archegonia, has been found, as in a species of Cycadinocarpus (fig. 

 210). In the figure cited it is evident that the endosperm has 

 encroached upon the nucellus almost to the testa, and that it has devel- 

 oped a characteristic endosperm beak which supports the settling 

 nucellar beak, as in Ginkgo, in which form Hirase aptly likens the 

 endosperm beak to a "tent pole." Two archegonia are evident in 

 the section, and opened into the archegonial chamber which sur- 

 rounded the base of the "tent pole" like a moat. This peculiar 

 endosperm beak is one of the several characters that show a close 

 connection between Cordaitales and Ginkgoales. 



