390 



PLANT MORPHOLOGY 



D -- H ^^-^ 6 



Fig. 333. Development of the embryo sac of Fritillaria biflora X200. A, entire ovule 

 with megaspore mother cell; B, 2-nucleate stage; C, first 4-nucleate stage; D, the four 

 megaspore nuclei beginning to divide; E, completion of division, resulting in second 

 4-nucleate stage; F, the two micropjlar nuclei being haploid and the two chalazal ones 

 triploid; G, the two micropylar nuclei and one of the chalazal nuclei dividing again; H, 

 mature embryo sac with egg, two synergids, and haploid polar nucleus at micropylar end 

 and triploid polar nucleus and two antipodal cells at chalazal end. 



