132 



GYMNOSPERMS 



which later gives rise to two sperms, while the cell beneath it divides 

 again, producing another body cell, and the process is repeated until 

 as many as 8 and sometimes even 1 1 body cells have been formed, 

 each of which produces two sperms. 



I'lG. 141. — Dioon ediile: two \oiin)^ sperms. Tlie nuclei of tlic sihtihs have become 

 larger, and, in the one at the left a part of the spiral band can be seen attached to the 

 beak of the nucleus; X350. 



Dr. DowNiE'" regards the generative cell as the primary sperma- 

 togenous cell, and the stalk cell as a spermatogenous cell still active 

 in Microcycas, but having lost the division potentiality in other 

 gymnosperms. This interpretation seems to be sound from the stand- 

 point of comparative morphology and phylogeny. 



Sperms of cycads are remarkably large (fig. 146). In Dioon edule, 



