WHITE— STUDIES OF INHERITANCE IN PISUAl 559 



height and flowering time, as did Keeble and Pellew. An Fo popu- 

 lation from such a cross gave 23 ED 189 ET : 76 LD:i83 LT 

 (Table I.). 



Interpretation. 



Tschermak has provisionally interpreted his results as due to 

 the presence and absence of two factors, with the possibility of there 

 being a third, although he states this character is probably much 

 more complicated. 



The two factors are a " Zug " or pulling factor and a " Treib " or 

 driving factor, there being possibly two of the latter. The " Zug " 

 factor produces intermediates with a tendency to be late-flowering, 

 while the " Treib " factor modifies the " Zug " f actoral expression 

 so as to give early flowering forms. By itself, it cannot alter the 

 status quo. In the absence of both, constant late-flowering forms 

 are produced. 



The second " Treib " factor postulated is a positive present in 

 all peas, giving constant lates in the absence of the other two factors 

 or constant earlies in the presence of the other factors. The various 

 varieties experimented with, on the two factor conception, would 

 be represented by f ormulfe as follows : 



Constant early AABB, 



Constant intermediate AAbb, 



Constant late aaBB or aabb. 



Combinations of AABB X aabb would give in E^ an interme- 

 diate AaBb. In E,. the expected ratio of early, intermediates and 

 lates would be 3:9:4. Eurther explanation is long and compli- 

 cated. In view of the numberless varieties with differences in the 

 length of time it takes them to reach the blooming period, it appears 

 to the writer that some cases should be of simpler composition than 

 others — the early, intermediate and late classes being interpretable 

 as combinations of a single pair of factors, which in E„ would give 

 a 1:2:1 ratio. 



Hoshino (40.5) also interprets his genetic data on time of flow- 

 ering by means of two factors, one of which, Lf (A), determines 

 the "proper" time of flowering in the late parent, while Ef (B) 

 modifies the expression of Lf toward earlier flowering, and is hypo- 



