568 WHITE— STUDIES OF INHERITANCE IN PISUM. 



with 8 very distinct varieties with green pods confirmed Mendel's 

 results. In some of these crosses, Tschermak obtained colored- 

 flowered, yellow-podded segregates which remained constant. 

 Yellow-pod segregates always bred true, while the green-pod Fo 

 segregates in F3 in some cases were constant, and in others gave 

 both green- and yellow-podded plants. 



Green pod X purple pod in F^ always gives all purple-podded 

 progeny (56, 86, 34, 90). In F,, Lock obtained five different types 

 of segregates — segregates with all purple pods, with all green pods, 

 and segregates having green pods with various degrees of purple col- 

 oring. Some plants were very faintly pigmented. Tschermak obtained 

 small F2 numbers — 10 purple in different degrees : 5 green. In F3, 

 the Fo purple-pigmented plants gave 34 purple : 27 green. Fruwirth, 

 on the other hand, obtained all green-pod progeny in Fj of two 

 crosses of green pod X purple or purple-splashed pod varieties, and 

 in Fo of one of them, 39 green-podded and 10 purple or purple- 

 splashed segregates were obtained. According to Fruwirth, purple 

 pod color is inherited independently of purple-specked seed coat 

 pattern. 



Yellow pod X purple pod gives in F^ (86) purple pod, which in 

 Fo gives purples or purple-splashed : yellow in an approximation 

 to a 9 :7 ratio. Yellow-podded segregates always breed true. 



No data have been pubHshed on crosses of F^ yellow and F, 

 green-podded segregates from combinations involving purple-podded 

 varieties. 



Interpretation. 



So far as our present data go, all green-pod varieties of peas 

 may be regarded as differing from yellow-pod varieties by the pres- 

 ence of a factor Gp. The factorial relation of purple-podded varie- 

 ties to green- and yellow-pod varieties cannot be cleared up until 

 more data are obtained. Tschermak regards purple-pod varieties 

 for the present as bifactorial, dift'ering from green- and yellow-pod 

 races by the presence of two factors (P^ and Po). Through the 

 presence of both of these factors purple-pigmented pods would 

 result. In the absence of either or both the plant has green or yel- 

 low pods. Possibly there is more than a bifactorial difference be- 

 tween purple- and yellow-podded varieties, but Tschermak's num- 



