dn 



FIG. 44. Development of ovule and embryo-sac of Shepherd's Purser 

 (Capsella Bursa-pastoris). The integuments are not shown. 1, Early 

 stage : e.m, archesporium or embryo-sac mother-cell. 2, The mother- 

 cell has divided once. 3 ? A second division has taken place. 4, The 

 lowest of the three cells, c (the embryo-sac), is obliterating the two 

 above it. 5, The nucellus disappears, except at the base ; the 

 nucleus of the embryo-sac has divided. 6, Each daughter-nucleus 

 divides again. 7, Four nuclei at each end of sac ; three at each end 

 have cells around them : c.a, egg-apparatus ; p, p^ upper and lower 

 polar nucleus ; an, antipodal cells. 8, The polar nuclei approach 

 each other ; s, s, synergidr: ; 0, ovum. 9, Fertilisation stage ; pp, 

 secondary nucleus, arising from fusion of polar nuclei. Magnified 

 about 200. (After Guignard.) 



