86 MASS. EXPERIMENT STATION BULLETIN 185. 



In Table XIV. are shown the results of crossing Burpee Stringless and 

 Golden Eyed Wax with two other black wax varieties, — Prolific Black 

 Wax and Currie. These crosses differ from those shown in the preceding 

 table in that two new colors designated as H and B make their appearance 

 in relatively small numbers. 



Burpee Stringless carries the yeUow-black modifier M and the deter- 

 miners F for coffee brown, and C for yeUow. Prolific Black Wax probably 

 carries the F and possibly C, though other crosses of this variety seem 

 to show that it lacks C, in which case its non-appearance here may be 

 explained by the small numbers involved. It also carries the black de- 

 terminer G and possibly another one, H, for olive brown, though the be- 

 havior of this color is not at all well understood. 



In other crosses of this table buff-colored beans (B) appear. According 

 to our hjT^othesis this can occur only when the modifier M is absent, or, 

 if present, only when aU determiners are absent. In these varieties M is 

 present, therefore they must carry no determiner in common. Golden 

 Eyed Wax carries the determiner C, and this must be absent in the vari- 

 eties Currie and Prolific Black Wax. The absence of B beans from the 

 F2 generation may easily be due to the small number involved. 



In one cross of Golden Eyed Wax with Currie, H beans appear, while 

 in the other none are recorded. This may be due to the absence of a de- 

 terminer for H in the strain of Currie involved. As elsewhere stated the 

 behavior of the type recorded as H is uncertain and not well understood. 

 The data presented in Table XIV. indicate the formula for Currie of 

 PTyZMm'OGFc, with the possible additional determiner H, and for 

 Prolific Black Wax, of PTyZMm'GFc and possibly the H in addition. 

 The latter may carry also the determiner C, preventing the appearance of 

 buff beans, but as other crosses indicate that it does not carry C, it is 

 regarded as more probable that the absence of B beans is due to the small 

 numbers involved. 



In Table XV. are shown the results of the crosses of Blue Pod Butter 

 with Burpee Stringless (coffee brown), and with two yellow seeded sorts. 

 All these crosses but one give black mottled beans in Fi. While none of 

 the mottled beans breed true in later generations, as has been already 

 explained, there have been many cases where solid black beans have bred 

 true. The appearance of these black beans is explained on the hypothesis 

 that Blue Pod Butter carries the black determiner G, but does not have 

 the yellow-black modifier M, and the lack of this prevents the G determiner 

 from acting. On crossing with a variety carrying M, the G takes effect, 

 producing a black or black mottled bean. In cross 16a no black beans 

 appear. It is probable that another strain of Blue Pod Butter which 

 lacked the G determiner was used in this cross. It must have carried the 

 determiner F, for F is always epistatic to C, and could not be carried by 

 Golden Eyed Wax. No B beans appear in F2, owing, doubtless, to the 

 small numbers, for they do come out in later generations as extractives 

 from F parents, and some of them breed true. 



