114 



THE LIVING CYCADS 



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Fig. 6o. — Dioon edule: upper part of ovule at time of fertilization. 

 The pollen tube on the left shows the body cell still undivided; in the 

 one on the right the body cell has just divided; the one in the middle 

 shows two sperms in the swimming condition; two empty pollen tubes, 

 with wavy margins, have shed their sperms; a sperm is about to enter 

 the egg at the right; at the left a sperm has already entered and can be 

 seen in the top of the egg. Magnified about 400 diameters. 



