MULTIPLE FACTORS 



231 



differ in several factors that affect their size. If the 

 parent strains were pure the Fi hybrids would all be 

 alike, or rather would show little if any more varia- 

 bihty than either parent stock, because all these Fi 

 plants receive the same contributions from the 



Fio. .56.— At loit, a flower of NicotiaiKi .ilMta firaiidifiora; at right N. 

 forgctiana; botwoc.n them are four F2 fiuwris, .showing the result of 

 seKregation both in the lengtli and the spread of the corolla. (After 

 East.) 



parents. But when in the gametogenesis of the Fi 

 plants these factors segregate, many new combina- 

 tions will be formed, and among them will be a few 

 combinations like those in the original varieties; 

 hence we expect in the F2 a wider variability, with a 

 return to the grand) )arental types in a certain \w\- 

 centage of the i)lant.s. East suggests that four 

 pairs of factors may cover the results in this instance. 



