SEED COAT COLOR IN GARDEN BEANS. b\) 



Beans classified as H appear in F2 in the crosses with Burpee Stringless 

 only, but they do appear scatteringly in later generations of most of the 

 other crosses. Too small numbers are involved to determine its nature 

 and relations. It is not always easy to separate the several colors F, C and 

 H in making field observations. These colors seem to develop in the ripen- 

 ing beans somewhat in order of their epistasis, the olive H first, and so on 

 up to the coffee brown, and even black, provided determiners for these 

 higher colors are present. The fact that several selfed plants recorded as 

 H gave rise to offspring made up partially or wholly of F beans in crosses 

 1 and 2 raises the suspicion that these parent plants really carried the 

 determiner F, but for some reason failed to develop their true color. Pos- 

 sibly the weakening effect of covering the plant, which has been already 

 discussed, may have had this effect. 



The yellow color G is more positively determined in the field, and the 

 records seem clear. Extracted C beans either breed true or yield B beans 

 in the proportions 3C:1B. According to our hypothesis there might be a 

 9:7 proportion in cases like this when the heterozygote is a hybrid, as 

 Mc mC. Such a heterozygote would be yellow, and would yield 9 yellow 

 to 7 buff. No such proportion is approached among the offspring of 

 G parents, but in the other columns are shown a few cases that approach 

 such a proportion. Their number is too few to be sure whether they are 

 9:7 or 3:1 proportions. The total numbers of such offspring in the table 

 are 172 G, F, H and C beans to 73 buff. This is a considerable excess of 

 buff beans, and supports the idea that some of these proportions are 

 really 9:7. If such cases do occur the buff beans would be of three kinds, 

 some lacking the modifier M, some the determiner and some lacking 

 both. This raises the question whether these can be distinguished from 

 each other. While this cannot be answered positively, we are quite sure 

 that more than one kind of buff beans does appear. Some further evidence 

 will be presented on this point in connection with a discussion of the 

 relations between seed coat and flower colors. 



In Table IV. are shown the results of crossing self-colored varieties 

 where mottled progeny resulted. This showed equal numbers of self- 

 colored and mottled beans, in harmony with the hypothesis of Emerson. 

 In Table XVI. are shown those crosses which involve Blue Pod Butter 

 and black wax varieties, separating the self-colored beans into black and 

 buff. These appear in approximately equal numbers and both breed 

 true. It was early observed that buff beans generally bred true in all 

 crosses, and comparatively few were planted. This accounts for the 

 small numbers given in the right-hand column of the table. Our records 

 show some half dozen plants scattered through the several crosses that 

 were called smoky black or brown. None of them were self-fertilized, 

 and it is impossible to say whether they represented types that appear in 

 very small proportion, whether they were mutations, or whether they were 

 the result of environmental conditions. We are inclined to attribute them 

 to the last-named influence. If the constitution of Blue Pod Butter is 



