146 



MORPHOLOGY OF GYMNOSPERMS 



brane, but could not determine whether it belonged to the sperms or 

 might be only the Hautschicht of the cytoplasm of the pollen tube. 

 In such a case the two sperms would simply become loosened from 

 the stalk cell and swim away (figs. 170-172). In Dioon edule, accord- 

 ing to Chamberlain (63), the division of the body cell gives rise to 



Fig. 173. — Dioon edule: photomicrograph of end of pollen tube, showing that 

 the two sperms are formed within sperm mother cells; the walls of the mother cells 

 can be seen between the sperms and surrounding them; X720. — After Chamberlain 

 (63)- 



two sperm mother cells, inside of which the sperms are organized 

 and from which they are discharged. This conclusion is based upon 

 an examination of both living material and sections. The photo- 

 micrograph reproduced in fig. 173 shows the two sperms within their 

 mother cells. 



In Cycas, Zamia, and Dioon two sperms are formed in the pollen 



