580 



THE AMERICAN NATURALIST [Vol.L 



of 269 piebald beans. It will be understood that each 

 row was planted from the offspring of a single plant. 

 Not all of these beans can be considered as belonging to 

 the F 2 generation. A portion of these certainly belong 

 to the F 3 and later generations. This question will be 

 considered further in a later paragraph. 



From this table it will be seen that only three kinds of 

 beans were obtained from these piebald seed. These 

 were piebald, Improved Yellow Eye and Old-Fashioned 

 Yellow Eye. This fact, in connection with the evidence 

 obtained from controlled pollinations as noted above, 

 make- it practically certain that these piebald beans are 

 hybrids between these two varieties of Yellow Eye beans. 



Further, with the exception of three small rows none of 

 of these piebald beans gave evidence of breeding true. 

 In each of these three cases some of the piebald beans 

 have split in later generations. Thus in pedigree No. 

 1294-5 the 1914 Bow 31 is the offspring of one of the five 

 piebald plants in the 1913 Row 88. It seemed possible 

 that this line was breeding true. However, the 1915 Row 

 58 is the offspring of a plant from Row 31 of the year be- 

 fore, and Row 58 gave all three types, so that both of the 

 preceding rows must have been heterozygous. If larger 

 numbers had been grown from the same seed they would 

 undoubtedly have thrown all three types. 



The evidence thus indicates that the piebald pattern is 

 the expression of the heterozygous condition of the fac- 

 torial difference between these two types of Yellow Eye 

 beans. A similar conclusion was reached by von Tscher- 

 mak (1912). He obtained spotted beans very similar to 

 our ' 1 piebald' 7 from crosses between eyed and white or 

 eyed and solid color beans. These piebald beans were 

 always heterozygous, throwing on the one hand a large 

 eye with regular outline corresponding with our Improved 

 Yellow Eye and on the other hand a small-eyed bean. 

 Judging from his figures (p. 208) von Tschermak's small- 

 eyed bean had nothing corresponding to the peculiar pat- 

 tern on our Old-Fashioned Yellow Eye. However, in 



