I20 



GYMNOSPERMS 



times hundreds of archegonia, some of them on the sides of the game- 

 tophyte, and some even at the base. They are often as crowded as 

 in the Cupressaceae. Dr. Lillian Reynolds,''"'' studying the de- 

 velopment of the archegonia in Microcycas, found the large numbers 

 reported by Caldwell, but found that only the group at the micro- 

 pylar end of the gametophyte progressed up to the ventral canal 

 mitosis, and that only in connection with this group was there any 

 archegonial chamber. 



//6 



Fig. 1 1 6. — Dioon edule: ovule soon after pollination, free nuclear stage of the female 

 gametophyte. — From Chamberlain, The Living Cycads"" (University of Chicago 

 Press). 



Fig. 117. — Dioon edule: the female gametophyte has become cellular throughout. — 

 From Chamberlain, The Living Cycads"" (University of Chicago Press). 



In Dioon edule the archegonium initials can be seen early in No- 

 vember (tigs. 1 18-122). They soon divide, forming the central cell 

 and the primary neck cell, which divides almost immediately, so that 

 December material shows the two neck cells characteristic of all the 

 cycads. 



The central cell enlarges rapidly without a corresponding increase 

 in the amount of protoplasm. Consequently, there is a large vacuole 



