FERTILIZATION 



299 



in one male nucleus than in the other, so that the two may appear quite 

 unlike during the later stages. Miss Welsford also sees in the male 

 cytoplasm certain granules which she thinks may represent the vestiges 

 of blepharoplasts. 



B 



FIG. 123. Fertilization in angiosperms. 



A, end of pollen tube from basal portion of style of Lilium auratum, showing two male 

 cells and tube nucleus. X 250. (After Welsford, 1914.) B, double fertilization in Lilium 

 canadense: male and female nuclei about to fuse in egg; second male and two polar nuclei 

 fusing at center of embryo sac; s, synergids, one degenerated; a, antipodals X 250. 

 C, fusion of sexual nuclei in egg of Lilium philadelphicum. X 1000. (After Weniger, 

 1918.) D, the second male and two polar nuclei in Lilium Martagon. X 750. (After 

 Nothnagel, 1918.) E, vermiform male nucleus in contact with egg nucleus in Triticum 

 durum. X 600. (After Sax, 1918.) F, spireme stage of triple fusion nucleus in Triticum 

 durum, showing distinctness of three chromatin contributions. X 750. (After Sax, 1918.) 

 G, inclusion of cytoplasm in fusing sexual nuclei of Peperomia sintenesii. (After Brown, 

 1910.) 



Fusion in Egg. As already stated, one male nucleus passes into 

 the egg and fuses with the egg nucleus. So far as observations enable 

 one to say, only the male nucleus, and no cytoplasm, enters the egg, a 

 point of much importance in connection with the transmission of heredi- 

 tary characters from the male parent. It would be a matter of extreme 

 difficulty, however, to demonstrate conclusively that in passing through 

 the egg membrane the male nucleus is absolutely freed of all adhering 

 cytoplasm or chondriosomes; and it must be admitted that such a 

 demonstration has not yet been given in any case. The fusion of the two 

 sexual nuclei probably occurs in most cases very soon after they come 

 in contact, though in certain forms the actual fusion is known to be 



