SYNGAMY 



237 



Fritillaria, in which Sax (1916, 1918) finds that fusion, though it usually 

 occurs in the reticulate stage, sometimes takes place after the thick 

 prophasic threads have been developed. Weniger (1918) reports that 

 in Lilium the egg nucleus is reticulate and the male nucleus in prophase 

 as they unite. Whatever the state of the nuclei at the time of their 

 fusion, all of the chromosomes, paternal and maternal, split longitudinally 

 in the first mitosis in the zygote, the daughter chromosomes so formed 











Fig. 144. — Syngamy in angiosperms. A, end of pollen tube from basal portion of 

 style of Lilium auratum, showing two male cells and tube nucleus. {After Welsford, 

 1914.) B, double fertilization in Lilium canadense; sexual nuclei about to fuse in egg; 

 second male and two polar nuclei fusing at center of embryo sac; s, synergids, one degen- 

 erated; a, antipodal cells. C, fusion of sexual nuclei in egg of Lilium philadclphicum. 

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

 {After Nothnagel, 1918). E, vermiform male nucleus in contact with egg nucleus in Triti- 

 cum durum. {After Sax, 1918.) F, spireme stage of triple fusion nucleus in Triticum 

 durum., showing distinctness of chromatic elements of the three nuclei. {After Sax.) 

 G, inclusion of cytoplasm in fusing sexual nuclei of Peperomia sintenesii; this seems to be an 

 occasional phenomenon with no special significance. {After W. H. Brown, 19186.) 



being distributed to the two resulting nuclei, just as in all the subsequent 

 divisions in the developing embryo. 



The time elapsing between pollination and the union of the gametes 

 varies greatly in different plants, but the variation shows no necessary 

 correlation with the length of their styles. The following examples" 

 may be cited: Zea Mays, 18 to 24 hours; Triticum vulgare, 18 to 20 hours; 

 Lilium philadelphicum, 60 to 72 hours; Phaseolus vulgaris, 8 to 9 hours; 

 Acer negundo, 40 to 72 hours; Monotropa unifiora, 5 days; Secale cereale, 



2^ See Schnarf (1929) for an extensive list with citations to literature. 



