SEED COAT COLOR IN GARDEN BEANS. 



73 



At least two of the white varieties used in this work, Davis Wax and 

 White Marrow, seem to carry the factors for mottUng, and in most cases 

 they have jielded in F2 mottled, self-colored and white beans in what is 

 probabI,y a 9:3:4 ratio. Crosses with these varieties are shown in Table 

 V. All extracted whites have bred true, and extracted self-colored beans 

 have either bred true or yielded self-colored and mottled beans in approxi- 

 mately a 3:1 ratio. In several cases mottled beans have been extracted 

 which bred true, thus indicating that in some cases at least both Davis 

 and Wliite Marrow carry both Y and Z ; that is, they are really mottled 

 beans lacking pigment. In cross 33a no mottled beans appear, probably 

 because Blue Pod Butter and the particular strain of Wliite Marrow 

 involved carry the same mottling factor, and both likewise lack the other 

 one. It is certain that a different plant of Wliite Marrow was used and 

 one from a commercial stock, while in 33 and 34, individuals of a selfed 

 strain were used, and this strain was not derived from the plant used in 

 33a. 



In the cross of Golden Eyed Wax X Wliite Marrow (Table V.) the 

 behavior as regards mottling is as expected from the above considera- 

 tions. In another cross of what were supposed to be the same varieties 

 no white beans appeared. The behavior of the progeny was exactly 

 what would be expected of a cross of Golden Eyed Wax X Warwick. 

 Warwick and White Marrow were grown next to each other in the row, 

 thus making it easy to make an error in obtaining blossoms. We are 

 therefore inclined to believe that the irregularity was due to such an 

 error in pollination. 



According to Emerson's theory of mottling all mottled varieties have 

 the constitution PYZ in which formula P indicates the factor for pig- 

 mentation and YZ the coupled factors for mottling. Non-mottled pig- 

 mented beans can have only one of these factors bearing either PYz or 

 PyZ. White beans may be either pYZ, pYz or pyZ. The possible re- 

 sults of intercrossing these types of beans are as follows : — 



