228 



REPRODUCTION 



em 



34 



FIG. 131. Stages in the formation of the megaspore, its germination, fertilization of 

 the egg and endosperm nuclei, and germination of fertilized egg and endosperm cells. A. 

 beginning of ovule at o; B, nu, nucellus; Ca, nu, nucellus, a, archesporium; in, forward 

 growth of tissue to form the integument; Cb, nu, nucellus; in. integument; D, more highly 

 magnified drawing of o in A showing archesporial cell at a; E, a, archesporial cell enlarged 

 and ready for division; nu, tissue of the nucellus; F, a, archesporial cell dividing, nu, nucellus; 

 G, row of four megaspores descended from the archesporial cell, only the upper one, in. 

 functional, the others soon to disintegrate; H, the megaspore, m, enlarging, the others 

 disappearing; /, nucleus of the megaspore divided into two, md; J, continued nuclear 

 division has resulted in eight, namely, three antipodal nuclei, aw, at the upper end of the 



