72 



MASS. EXPERIMENT STATION BULLETIN 185. 



Extracted self-colored individuals have bred true, and no unpigmented 

 beans have appeared. We may note at this point that Blue Pod Butter 

 is one of the parents of all these crosses. The explanation of this is 

 that Blue Pod Butter is the only self-colored bean bearing the factor Y, 

 all other self-colored varieties carrying the other factor for mottling, 

 designated as Z; and as, according to Emerson's theory, mottling can 

 result only when Y and Z are both present, the variety named is 

 the only self-colored variety that can produce mottling when crossed 

 with the other self-colored variety used. While the proportion 1:1 is 

 held quite closely when the total numbers of reciprocal crosses are con- 

 sidered, it may be noted that in all cases except the crosses involving Blue 

 Pod Butter with Golden Eyed Wax and Challenge Black Wax there is an 

 alternate preponderance of mottled and self-colored beans in the two 

 members of the reciprocal crosses, a fact that may have a significance, 

 or be onlv a chance occurrence. 



Table V. — Crosses of Self-colored with White Beans yielding Mottled 



Progeny. 



