444 BOTANICAL GAZETTE [December 



judging from the number of cells, does not appear to divide and form 

 new cells after the first division of the megaspore mother cell, but 

 rather, the megaspore by dividing first into two cells (fig. 15), and 

 then into four cells (fig. 16), develops in such a manner as to pro- 

 trude from the region of the "nucelle." The embryo sac is long 

 and narrow in its chalazal part, and is enlarged in the micropylar 

 end. After the embryo sac reaches the 4-cell stage, as in fig. 16, 

 the nuclei migrate, and the two micropylar nuclei go to the micro- 

 pylar end of the sac and arrange themselves one on each side of the 

 sac. The nucleus closest to the micropylar end of the embryo 

 sac now divides to form two nuclei, from which the cells of the pear- 

 shaped synergids arise. The other micropylar nucleus divides to 

 form the egg nucleus and the micropylar polar nucleus. The 

 nucleus of the egg had about the same diameter as the synergid 

 nuclei when observed, while the polar nucleus had about twice the 

 diameter of any of the other three micropylar nuclei. 



The other two of the four nuclei migrate to the chalazal end 

 of the sac. One of the two chalazal nuclei is found almost at the 

 very tip end of the embryo sac, while the other is located just 

 above it. 



It is here that both of these nuclei divide to form the four 

 antipodal nuclei. When the two nuclei divide, their spindles form 

 with the poles toward the ends of the embryo sac rather than 

 crosswise. The three lower nuclei (fig. 18) Jater become the three 

 degenerating antipodal cells. They degenerate rapidly while the 

 upper nucleus migrates toward the center of the embryo sac, 

 and as it migrates, it greatly enlarges and comes to be as large as 

 the polar nucleus from the micropylar end of the sac. The micro- 

 pylar polar nucleus and the chalazal polar nucleus now fuse. In 

 the stage before fusion, the nucleoli of both are very prominent 

 (fig. 21), and the nucleus of each is somewhat more than two 

 diameters of the nuclei in the synergids. The large secondary 

 endosperm nucleus now migrates upward toward the central part 

 of the embryo sac, where it is found later, gorged with food. 



In Digitalis purpurea Balicka-Iwanowski observed remnants 

 of the antipodals, while in Linaria Cymbalaria the antipodals are 

 distinct and persist until the complete formation of the chalazal 



