542 



STUDIES IN FOSSIL BOTANY 



transversely elongated, so as to partially close the 

 passage (Fig. 195, B, g). Possibly this may have 

 been an arrangement for shutting the entrance to the 

 pollen-chamber after pollination had been effected. 



Fig. 195. — Cordaiantlius Grand ' Eitryi. A. Longitudinal section of female flower, show- 

 ing one ovule, just pollinated, d, axis ; b, bracts ; c, integument ; tt, nucellus ; c.p, 

 pollen-chamber ; g, canal of pollen-chamber ; /, pollen-grains in chamber, and/', in 

 canal, x 24. B. Canal of pollen-chamber enlarged, g, dilated cells, enclosing the 

 canal, o ; p, p', two pollen-grains in the canal ; ex, outer membrane of pollen-grain ; 

 in, group of prothallial or antheridial cells within the grain. :■: 150. C. Grains of 

 pollen, showing internal cells ; the smaller grain from an anther, the larger from the 

 canal of an ovule. >; about 100. All after Renault. 



The pollen-chamber is, as we have already seen 

 (Chap. X. p. 392, and Chap. XI. p. 453), a general feature 

 in Palaeozoic seeds. The pollen-chamber of Trigono- 

 carpus, for example, among the Pteridosperms bears 

 a rather close resemblance to that of a Cordaitean seed 

 (see Fig. 170, p. 454). The Cycadaceae and Ginkgo 



