176 



PLANT-LIFE 



embryo-sac, e, e, is the megaspore which remains en- 

 closed in the ovule (the megasporangium). Some 

 smaller cells occur in the embryo-sac; of these, three, 

 known as " antipodal cells," represent the prothallus; 

 they are found farthest from the micropyle. Three other 

 cells at the micropyle end are the egg-apparatus, one 

 of them being the ovum, or egg-cell. This is the cell 

 which becomes fecundated by the male element, and 



h - 



FIG. 59. WALLFLOWER. LONGITUDINAL SECTION THROUGH AN OVULE AND 

 PART OF THE OVARY WALL. (AFTER D. H. SCOTT.) x 50. 



A, A hair; ov, ovary wall;/, funicle of ovule; ch, chalaza; n, nucellus; in v 

 inner integument; in 2 , outer integument; m, micropyle; e, e, embryo-sac; 

 p.t., pollen tube. 



ultimately develops into an embryo. In the Wallflower 

 several embryo-sacs occur in the same ovule; it is un- 

 usual for them to be so numerous ; in most plants only 

 one is found. 



In outlining the story of Selaginella (p. 166), we noted 

 that the megaspore, during the early stages of germina- 

 tion, remains in the sporangium, and while there it is 

 nourished by the sporophyte; ultimately, however, it is 



