WHITE— STUDIES OF INHERITANCE IN PISUM. 561 



green podded F, segregates tested in F3, 14 bred true, while 34 gave 

 both yellow and green foliage and podded F3 progeny, the total 

 ratio being 427 GF: 146 YF. 15 F^ yellow-foliage segregates gave 

 all yellow-foliage F3 progeny. F^ gave no exceptional results. 



Interpretation. 



Varieties with green foliage and green pods differ from those 

 with yellow foliage in the form investigated by the presence of the 

 factor O. Hence all varieties of peas investigated with green foliage 

 are OO, while those with yellow foliage are 00. 



13. Tendrilled and Non-Tendrilled Leaves. 



With one exception, all cultivated varieties of peas have leaves 

 in which part of the pinnae have been replaced by tendrils. This 

 one exception — the Acacia variety — has wrinkled seeds and no ten- 

 drils, the place of the tendrils being taken by extra pinnje. The 

 variety breeds true as regards both the characters mentioned. Its 

 origin is unknown, though the variety was first studied by Vilmorin 

 (89,90). 



Results from Crossing. 



Tendrilled, round seed X Acacia, wrinkled seed gave in F^ all 

 tendrilled, round-seeded progeny. In some crosses, the F^ tendrils 

 are slightly strapped-shaped, especially in the youngest tendrilled 

 leaves. Otherwise dominance of tendril is complete. 



The Fi plants bore Fo round and wrinkled seeds in the usual 3 : i 

 proportions and the F2 proportion of tendril and Acacia plants was 

 as expected, approximately 3:1. In such a cross, providing these 

 two pairs of characters were independently inherited, four classes 

 in a ratio of 9:3:3:1 would be expected. When the seed and leaf 

 characters were thus considered the four expected classes were 

 found, but the proportions were awry, the two middle classes being 

 all but absent. In other words, the Fo round seeds gave almost ex- 

 clusively tendrilled plants, while the F^ wrinkled seeds gave practi- 

 cally all Acacia or non-tendrilled plans, showing that round and 

 tendrils, wrinkled and Acacia were almost completely linked or 

 coupled together in their inheritance. 



