264 



J^EDUCTIOX 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 o-g^, 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- 



i-d^!v-i; 



>^**: 



•tPW^:. 



C 









E 



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 {Liliinii). B. Final anaphase of second division (Podophyllum'). 



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



D. Embryo-sac after completion of tlie first nuclear division (Li/iinii). 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, synergidse. (For further details, see Figs. 133, 134.) 



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

 three " 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 



