THE FEMALE GAMETOPHYTE 



127 



7 had organized into cells (four looking like synergids, two looking 

 like eggs, and one of an undecided nature) and 2 resembled polar 

 nuclei; antipodals were absent. 



Fagerlind's (1939c) observations differ from those of both Stenar 

 and Eysel. The megaspore mother cell has a highly vacuolated 

 cytoplasm (Fig. 82 A). u As a result of the first division, 2 nuclei 

 are formed of which the lower promptly degenerates and is reduced 



Fig. 82. Development of embryo sac in Limnanthes douglasii. A, megaspore 

 mother cell. B,C, two-nucleate embryo sacs ; note degeneration of primary chalazal 

 nucleus. D, three-nucleate stage originating by division of primary micropylar 

 nucleus. E, division of micropylar nucleus. F, embryo sac piercing the nucellar 

 epidermis; note two nuclei at micropylar end, one nucleus in middle, and degene- 

 rated nucleus at chalazal end. G, mature embryo sac showing egg apparatus, 

 upper polar nucleus, lower polar nucleus (?), and degenerating antipodal cell. 

 (After Fagerlind, 1939c.) 



to a densely staining homogeneous blob which lies at the bottom 

 of the embryo sac and takes no further part in the development 

 (Fig. 82B-C). The upper nucleus divides to form 2 daughter nu- 

 clei, of which the lower is much smaller and usually incapable of 

 further division (Fig. 82D). Following meiosis, we thus have a 

 3-nucleate stage showing a micropylar nucleus, a middle nucleus, 

 and a chalazal nucleus. Of these the micropylar nucleus divides 



11 In the majority of angiosperms vacuolation takes place only after the meiotic 

 divisions are over. 



