THE WHITE LILY 



187 



g.n 



o. n. 



itself to the two polar nuclei, which have approached 

 each other, but not yet fused (Fig. 86, g.n. t p v p 2 ). 

 Ultimately all three nuclei unite into one, so that the 

 secondary nucleus of 

 the embryo-sac is the 

 product of a triple 

 fusion, one of the com- 

 ponent nuclei belong- 

 ing to the male, and 

 two to the female 

 parent. It is to this 

 triple union that the 

 endosperm owes its 

 origin. 



Thus fertilisation in 

 Angiosperms is double, 

 the one act giving rise 

 to the embryo, the 

 other to the endosperm. 



The synergidse, hav- 

 ing done their work, 

 which probably con- 

 sists in guiding the end 

 of the pollen-tube to 



ji _ i. FIG. 87. Part of the embryo-sac of a 



the OVUm, now dlS- Lily, just after fertilisation, s, 5, re- 

 mains of the synergidoe ; g.n, gener- 

 ative nucleus, o.n, nucleus of ovum 

 (these are now closely united) ; 17.0, 

 vacuoles, e.n, e.n, endosperm nuclei 

 in course of division. Magnified 

 about 250 diameters. (After Guig- 

 nard.) 



appear. The antipodal 

 cells also undergo no 

 further development. 

 The embryo-sac is in 

 future shared between 



the embryo and the 

 endosperm, which latter structure is much more im- 

 portant here than in the Wallflower. 



f. Development of the Embryo 

 We need only describe fully those points in the 

 formation of the embryo in which the monocoty- 



