GNETALES— EPHEDRA 



379 



At the time of pollination, the 

 pollen grains fall on the pollina- 

 tion drop and are drawn down 

 the long micropyle. By this time 

 such a deep pollen chamber has 

 been formed by the breaking, 

 down of cells in the upper part 

 of the nucellus that the pollen 

 grains fall directly upon the fe- 

 male gametophyte. There would 

 be no place for a pollen tube, 

 were it not for the very long 

 neck of the archegonium. The 

 short pollen tube forces its way 

 through the neck of the archego- 

 nium and discharges all four of 

 its nuclei into the egg. 



Whether there is any "double 

 fertilization," like that in the an- 

 giosperms, is questionable; but 

 several observers have noted di- 

 visions at the top of the fertilized 

 egg, as well as at the bottom. 

 Land^'^^ found jacket cells disin- 

 tegrating at the time of fertiliza- 

 tion, so that their protoplasm and 

 nuclei mingled with those of the 

 egg. The second male nucleus 

 and ventral canal nucleus were 

 also in this region. As the ferti- 

 hzed egg nucleus divided, there 

 were also numerous divisions at 

 the top of the egg. These small 

 cells are soon absorbed by the 

 growing embryos, functioning 

 like the endosperm of angio- 

 sperms, and LanD'^^' believes 



Fig. 361. — Ephedra trif urea: fertiliza- 

 tion: pt, pollen tube; 0, egg nucleus; Wi 

 and W2 sperms; nii is fusing with the 

 egg nucleus; v, ventral canal nucleus; 

 X215. — After Land.JS!' 



