204 GENETICS AND EUGENICS 



linked with flower color or with the chief factor for flowering 

 time) will account for the case. In accordance with this 

 view, four true-breeding combinations of the factors for 

 flowering time might be expected, and it is possible that their 

 modes fall in Table 32 on 35 days, 40 days, 44 days, and 54 

 days respectively, all of which show high frequencies. An- 

 other possibility is that several modifying factors acting in 

 various combinations produce the wide ranging group of 142 

 ** constant" intermediate families and that linkage among 

 these modifying factors is responsible for the apparent dis- 

 continuity between the intermediate and the early and the 

 late groups. Certainly more than one supplementary or 

 modifying factor is in evidence. For it is to be remembered 

 that in Table 32, the F4 distribution is not that of individual 

 plants varying round particular modes, but each frequency 

 indicated is itself the mode of a family, ** constant as to that 

 particular modal length of time between sprouting and 

 flowering. Accordingly the ''constant" varieties resulting 

 from the cross are not four only, as a two factor scheme would 

 demand, but their number is very great, since they range 

 with only two apparent breaks all the way from the original 

 early to the original late variety. Such a result could be 

 produced only by numerous modifying factors, which in 

 action supplement, or else inhibit, the action of the chief 

 gene for flowering time so clearly linked with red flower 

 color in transmission. No other "factorial" explanation 

 seems admissible. 



