GNETALES— EPHEDRA 



377 



When the nucleus of the cen- 

 tral cell divides, no wall is formed 

 between the ventral canal nu- 

 cleus and that of the egg. The 

 ventral canal nucleus may then 

 move down with the egg nucleus, 

 or may remain at the top of the 

 egg- 



FERTILIZATION 



A dense mass of cytoplasm, 

 which is evident below the nu- 

 cleus of the central cell, becomes 

 denser, surrounds the egg nu- 

 cleus, and extends for a long 

 distance below it as fertilization 

 takes place (fig. 361). Similar 

 masses have already been noted 

 sperm nuclei of conifers. 



Fig. 358. — Ephedra irt'furca: A, pollen 

 grain just before formation of pollen tube; 

 the nucleus of the body cell is dividing to 

 form two sperms; B, pollen tube: Wi and 

 W2, the two sperms; s, nucleus of stalk 

 cell; /, tube nucleus; Xsoo. — After 

 Land."** 



in connection with both egg and 



A B 



Fig. 359. — Ephedra trifnrca: A, row of four megaspores, in which the lower mega- 

 spore is enlarging, the one above it is breaking down, and the mitosis for the formation 

 of the other two megaspores is in late telophase; B, simultaneous free nuclear division to 

 form the 64-nucleate stage of the female gametophyte; m, megaspores; Xsoo. — After 

 LAND.338 



