264 



REDUCTION 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 egg, the other three corresponding to 

 the polar bodies in the animal egg, though they here continue to 

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





c 





(y ■;>-!# 



^m 



rf 







B . 



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

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

 ' cells) just after the first division {Lilium). B. Final anaphase of second division {Podophyllutn). 



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



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

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

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



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

 three "antipodal cells" (which like the synergidse 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 



