SEED COAT COLOR IN GARDEN BEANS. 99 



frequent and possibly a constant character of beans of this class. At 

 any rate, we have here a peculiarity which would doubtless yield interest- 

 ing results on further and more specific investigation. 



Reciprocal crosses of Challenge Black Wax and Davis Wax yielded 

 complicated progenies. Dark mottled beans appear because the former 

 variety carries the factor O for dark mottling, which acts with YZ from 

 Da^^s Wax to bring about this result. Challenge Black Wax carries the 

 modifier M, and Davis Wax brings in M', so that we get beans of both 

 the yellow-black and red series. Owing to the complicated nature of the 

 progeny of this cross it is not shown in tabular form. 



Crosses involving White Marrow. 



The only other white variety that has been used at all extensively is 

 White Marrow. The color pattern factors are rather complex, and the 

 pigment factors much more so. Owing to this the crosses of White Marrow 

 with the several varieties used will be taken up one by one. Apparently 

 White Marrow carries several pigment modifiers and determiners in a 

 latent condition, owing to the absence of the pigmentation factor P. 

 When it is crossed with another variety carrying P, and perhaps several 

 additional modifiers and determiners, we have very many classes of 

 beans which are, extremely difficult to segregate. 



Crosses of White Marrow and Blue Pod Butter. — Three crosses of these 

 varieties have been made, including reciprocals. As previously indicated 

 (page 73), the Fi beans have light red (D) stripes and splashes on the 

 usual buff (B) ground color. In the next generation these split up, show- 

 ing, in addition to the two colors mentioned and the parent forms, con- 

 siderable numbers of coffee-brown (F) and yellow (C) beans. No black 

 beans have appeared in this cross, a fact that may be explained on the 

 hypothesis that the particular strain of Blue Pod Butter used lacked the 

 factor G. 



We have been led to conclude that Blue Pod Butter lacked both modifiers 

 M and M'. The appearance of both series of colors in the progeny of this 

 cross leads to the conclusion that White Marrow carries both modifiers 

 in an inactive state, owing to the lack of the factor P. When both are 

 present the M' is epistatic to M, and the beans are classified as of the 

 red series. 



Beans showing the dark red color have yielded in some cases only the 

 parent color (E), and in other cases various combinations of dark red 

 (E), light red (D), yellow (C), buff (B) and white, but we have no record 

 of coffee-brown beans (F) from this parentage, though they do appear in 

 small numbers from light red (D) parents. Yellow (C) parent plants 

 yield progeny of similar color, and, in addition, buff (B) or white or both 

 in subordinate numbers. In a few cases our records show light red (D) 

 beans in small numbers, which occurrences are difficult to explain. They 

 are rather too frequent to be mere accidents. Further investigation 

 should lead to interesting results. 



