THE FEMALE GAMETOPHYTE 



97 



totic divisions of the polar nucleus, and in one embryo sac as many 

 as 140 nuclei were formed by this method. In a few instances he 

 found a synergid containing about 20 nuclei. In Zauschneria lati- 

 folia (Johansen, 19316) the nuclei of the nucellar cells are said to 



B C D E F 



Fig. 62. Development of embryo sac in Oenothera suaveolens. A , tetrad of mega- 

 spores; both micropylar and chalazal megaspores are enlarging. B, embryo sac 

 formed from micropylar megaspore; the three chalazal megaspores in process of 

 degeneration. C, embryo sac formed from micropylar megaspore; one of chalazal 

 megaspores has also developed up to two-nucleate stage. D-F, twin embryo sacs 

 formed by concurrent growth of two megaspores. (After Hoeppener and Renner, 

 1929.) 



migrate into the embryo sac to form a variable number of bodies 

 looking like micronuclei of different sizes. 



Embryo sacs with fewer than 4 nuclei are rare, but in Hartmannia 

 tetraptera (Johansen, 1929) and Jussieua repens, Khan (1942) saw 

 two 3-nucleate embryo sacs having a single synergid, an egg, and a 

 polar nucleus. Their origin is probably to be explained by a lack 

 of division of the primary synergid nucleus of the 2-nucleate stage. 



