Dec. 6 , 1915 
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 
V79X113=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 = 1. 42 
Quotient of extremes of long-podded plants. 113-^-79—1. 43 
The standard deviation in the second generation was: 
Short Dong 
pods. pods. 
I 9 IO. 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 E 2 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 Dong 
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 Nicotiana 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 linkage 
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 
Dong 
of long to 
pods. 
pods. 
short pods. 
Mm. 
Mm. 
1910. 
. 24 
32 
I * 33 
1912. 
34 
I- 55 
