126 INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



reduced size of the nuclei at the chalazal end. Eysel (1937) con- 

 firmed this report but noted an occasional reduction in the number 

 of nuclei at the chalazal end of the embryo sac, owing to a failure 



H G F 



Fig. 81. Development of embryo sac in Plumbago capensis. A, two-nucleate 

 stage derived from first division of megaspore mother cell. B, four-nucleate stage. 

 C, all four nuclei dividing; one of the mitotic figures is oriented at right angles to 

 plane of sectioning. D, eight-nucleate stage, showing cutting off of egg cell. E, 

 differentiation of the four polar nuclei. F, fusion of polar nuclei. G,H, later 

 stages, showing egg at micropylar end and secondary nucleus in center. The two 

 lateral cells in G are derived from nuclei which ordinarily disappear in earlier stages. 

 (After Haupt, 1934.) 



of the basal nucleus of the 4-nucleate stage to undergo the last 

 division. In other cases he observed a disappearance of the wall 

 separating the megaspore mother cell from the nucellar cell situated 

 directly below it and the consequent incorporation of the latter 

 into the embryo sac. One embryo sac showed 9 nuclei, of which 



