930 
Journal o f Agricultural Research 
Vol. XXX, No. 10 
This formula, in independent inheri¬ 
tance, gives 1:1, or the ratio of the 
gametes YE to Ye and ve to vE. 
In the case of linkage, the formula in 
the bracket will equal the noncrossover 
gametes in relation to one crossover 
gamete when the factors Y and E 
enterjthe cross from one parent and v 
of linkage with 42 per cent crossover 
the fit is unusually good, X 2 being less 
than unity (Table XXII). 
This method of deriving gametic 
ratios and crossover percentages may 
prove of considerable value for those 
cases in which a selection is made in 
F 2 for noncorrelated characters. The 
12 15 IQ 2/ 24 27 
Fig. 1.—Distribution for Helminthosporium reaction of F 3 lines homozygous 
for other characters, cross SvanhalsXLion, 1923 
and e from the other. As selection was 
made for the characters 2-rowed and 
6 -rowed and the number of families in 
the 6-rowed group is different from the 
number in the 2-rowed group, the for¬ 
mula should be applied to each group 
separately and the two results averaged. 
When the observed results are com¬ 
pared to calculated results on the basis 
fact that it has been valuable in this 
one case is considered sufficient justi¬ 
fication for including it in this dis¬ 
cussion. 
Reaction to helminthosporium in 
RELATION TO OTHER CHARACTERS.^- 
Considerable variability is found in the 
reaction of a variety, even a pure line, 
to Helminthosporium sativum. For this 
