LUTHER BURBANK 



But the hereditary factors or "determiners" 

 that make for whiteness, though momentarily sub- 

 ordinated, are not eliminated, and half the germ 

 cells produced by the hybrid generation in which 

 blackness is dominant, will contain the factor of 

 whiteness, whereas the other half contain the 

 factor of blackness. And when in a successive 

 generation a germ cell containing the factor of 

 whiteness unites with the germ cell of another 

 plant similarly containing the factor of whiteness, 

 the offspring of that union will be white, their 

 organisms inheriting no factor of blackness 

 whatever. 



It may chance, however, that for many succes- 

 sive generations a germ cell containing only the 

 factor of whiteness fails to mate with another 

 similar germ cell and so no white-fruited progeny 

 is produced. In such a case generation after gen- 

 eration the white factors continue to be produced 

 in the germ cells, but the union with a germ cell 

 containing the black factor obscures the result just 

 as in the case of the first cross, because the factor 

 of blackness continues to be dominant. 



But, however long delayed, when a cell con- 

 taining the white factor or determiner does mate 

 with a similar cell, the offspring is white and — ^in 

 the older terminology — reversion or "atavism" is 

 manifested. 



[64] 



