PHENOMENA OF INHERITANCE 263 



when these were crossed a remarkable thing 

 occurred for the progeny "instead of being 

 white were purple like the wild Sicilian plant 

 from which our cultivated sweet peas are de- 

 scended." This is apparently a typical case 

 of reversion and its cause was found in the 

 fact that at least two factors are necessary in 

 this case for the production of color, a pig- 

 ment factor R and a color developer C. One 

 of these was lacking in each of the white 

 parents, their gametic formulae being Cr and 

 cR, but when these two factors came together 

 in the offspring a purple-flowered type was 

 produced with the somatic formula CcRr. 

 These F x plants produced colored and white 

 F 2 plants in the proportion of 9 colored to 7 

 white and the colored forms were of six dif- 

 ferent kinds (Fig. 55). For the production 

 of these six colored forms five different factors 

 must be present in the gametes, according to 

 Punnett, viz. : ( 1 ) a color base R, ( 2 ) a color 



developer C, (3) a purple factor P, (4) a light 

 wing factor JL, (5) a factor for intense color 



I. When all of these factors are present the 



result is the purple wild form with blue 



