Dec. 6, 191S Inheritance of Length of Pod in Certain Crosses 413 



The square root of the product of the extremes should give the means 

 nearly and the grandparental means more nearly. 



V53X 75=63. o Mean=62. 7 Grandparental mean=62. 8 

 •^79X113=94.5 Mean =94. 7 Grandparental mean=94. 5 



Lastly the combined multiplying value of all the minor factors (when 

 double) is given thus : 



Quotient of extremes of short-podded plants 75-^53 ==i- 42 



Quotient of extremes of long-podded plants 113-5-79=1. 43 



The standard deviation in the second generation was: 



Short Long 

 pods. pods. 



1910 *• 5-1 7-4 



1912 5. 2 6. 8 



That the standard deviation of the long-podded is greater than that 

 of the short-podded plants is in agreement with the hypothesis that the 

 minor factors act as multipliers. If E is completely dominant, there is 

 no difference in the action of Ee and Eg to increase the standard deviation 

 of the long-podded plants. The ratios of the two standard deviations in 

 each of the two crosses (1.4 and 1.3) are not quite 1.5, as theory would 

 seem to demand if all the variation were genetic. (See, however, below.) 



The coefficients of variation were : short Long 



pods. pods. 



1910 8. 2 7. 8 



1912 8.3 7.2 



If the variation were purely genetic, these coefficients should, I think, 

 be nearly equal. East (6), however, gives the variation coefficient of 

 the corolla-tube lengths of two parent lines of Nicoliana spp. as 8.9 for 

 the short-flowered (170) plants and 6.8 for the long-flowered (167) plants. 

 This variation was presumably not genetic. Judging from this, any 

 modifications would tend to increase the coefficient of variation of the 

 short-podded more than that of the long-podded plants. Hence, it is pos- 

 sible that the slight lowering of the standard deviation of the long-podded 

 plants from the theoretical 1.5 to 1.4, or 1.3 times that of the short- 

 podded plants, is an effect of modifications. Hence, this result does not, 

 I think, disagree with the hypothesis that the factors act as multipliers. 



That neither short-podded nor long-podded second-generation plants 

 show a significant increase in either range or standard deviation by more 

 than doubling their number seems to indicate that the genetic series can 

 be fully developed with about 50 plants. But the absence of Unkage 

 has not been proved, and until this has been done no definite deductions 

 as to the number of minor factors can be made. 



The ranges are : Ratio 



Short Long of long to 



pods. pods. short pods. 



Mm. Mm. 



1910 24 32 1.33 



^912 22 34 1.55 



