98 



MASS. EXPERIMENT STATION BULLETIN 185. 



many self-colored as mottled. If there is a factor X in Creaseback which 

 inhibits the expression of mottling as previously suggested, the following 

 gametes should be formed: PYZX, pYZX, PyZX, pyZX, PYZx, pYZx, 

 PyZx, pyZx. The zygotes formed would yield 9 mottled without X, 27 

 withX; 12 self-colored and 16 white. The 27 "mottled" beans with X 

 do not show mottling, making a to^al of 39 self-colored, 9 mottled and 

 16 white, or nearly four times as many self-colored as mottled. Of the 

 mottled beans 6 should show colors of both series, and 3 those of the red 

 series only, which are the actual numbers shown in the F2 generation of 

 this cross. 



Crosses involving Davis Wax. 

 As has already been shown, Davis Wax, a non-pigmented bean, carries 

 factors for light mottling which appear as soon as pigment is supplied. 

 When crossed with Blue Pod Butter the Fi generation is light mottled, 

 like beans of the Horticultural group. In F2 there are produced light mot- 

 tled, buff and white beans in the proportion, presumably, of 9:3:4. In 

 later generations these behave as shown in Table XXII. It is possible 



Table XXII. — Crosses involving Davis Wax. 



to derive from this cross light mottled races that breed true as well as 

 the parent types, as is shown in the table. No black beans appear, as the 

 modifier M is not present. 



Among these light mottled progeny there appear some plants that 

 produce what seem to be bud sports, in which the darker reddish color 

 predominates over the surface of the bean. These may appear as single 

 pods or as branches bearing several pods, and rarely a portion only of 

 the beans in a single pod is affected. If these dark mottled beans are 

 planted they breed true to seed coat color, while the plants with light 

 mottled seed may breed true in this character, or may give rise to plants 

 bearing bud sports as before. Limited observations suggest that these 

 sporting plants exist in definite proportions. The fact that such plants 

 have appeared so often in the breeding work here reported, and that dark 

 mottled beans are frequently seen in seed of varieties of the Horticultural 

 type offered for sale, suggests that this peculiarity of bud sporting is a 



