206 



The Journal of Heredity 



THE RESULT OF CROSSING EYED BEANS WITH WHITE 



Figure 7. The first generation is dark mottled, and in the second are found mottled, 

 solid colored, eyed, and white beans. The fact that crossing two light colored strains pro- 

 duces such dark beans is accounted for by assuming that the white parent carries an "Ex- 

 tension factor" that spreads the pigment, confined in the eyed parent to the region of the 

 hilum, over the entire seed. Two or more extension factors may act with different colors 

 of pigment, so that various patterns, with mottled or solid color backgrounds, occur. Photo- 

 graph by C. H. White. 



factor.s restilt in a character interme- 

 diate between the parents or resem- 

 l)ling one parent or the other. In this 

 cross of the eyed beans the factors 

 in a heterozygous condition not only 

 cause a great increase in area or 

 amount of pigmentation but also cause 

 an entirely new eye pattern. 



Eyed and White Beans 



Crosses of eyed beans with white 

 beans have given variotis types of 

 segregation in the second generation. 



In the cross /. Y. E. X White 1333. 

 the first generation was dark mottled 

 and the second generation gave a ratio 

 of 27 mottled: 9 solid: 12 eyed: 16 

 white. When two extension factors 

 are present one factor may extend one 

 class of pigments while the other ex- 

 tends another pigment, so that we may 

 get an eye pattern on a solid or 

 mottled background. This type of 

 pattern is shown in the last bean of 

 the eyed series in Figure 7. Usuall}^ 

 the eye is yellow or black while the 



