264 



KEDUC710X OF THE CHROMOSOMES 



the four primary cells of the embryo-sac (Fig. 132); and these two 

 divisions undoubtedly correspond to the two maturation-divisions in 

 animals. In the female, as in the animals, only one of the four 

 resulting cells gives rise to the (i<^^, the other three corresponding to 

 the polar bodies in the animal (t'^^^j:,, though they here continue to 

 divide, and thus form a rudimentary prothalHum.^ The first-men- 



\\ ■ 



7 



A 



^c- 





C 



' iV^:- 





m^^ 



... IV 



^ 



"4. ^ - • ■ . 



-V 



b-,.--'/ 



F 



E 



Fig. 132. — General view of the maturation-divisions in flowering plants. [MOITIER.] 

 A-C, in the male; D-F, in the female. A. The two secondary spermatocytes (pollen-mother- 

 cells) just after the first division (Liliurn). B. Final anaphase of second division {Podophyllum^. 



C. Resulting telophase, which by division of the cytoplasmic mass produces four pollen-grains. 



D. Embryo-sac after completion of the first nuclear division {Liliuni). E. The same after the 

 second division. F. The upper four cells resultin.; from the third division {c/. Fig. io6) : o, ovum; 

 /, upper polar cell ; s, synergida;. (For further details, see Figs. 133, 134.) 



1 Of these three cells one divides to form the "synergidre," the other two divide to form 

 thriee "antipodal cells" (which like the synergida:; finally degenerate) and a "lower polar 

 cell." The latter sooner or later conjugates with the " upper polar cell " (the sister-cell of 

 the egg) to form the " secondary embryo-sac-nucleus," by the division of which the endo- 

 sperm-cells arise. Of the whole group of eight cells thus arising only the egg contributes 



