34 
Journal of Agricultural Research voi. xxix, no. i 
The data show a wide range in varia¬ 
tion in the yield of F 2 plants. The 
number of parent plants threshed for 
comparison is small, especially at St. 
Paul. The average yield, standard 
deviation, and coefficient of variation 
of F 2 hybrids and parents are shown in 
Table XXIV. It appears important 
that at Mandan the average yield of 
the hybrids exceeds that of both parents 
tion apparently is the best measure of 
variability. It shows at both points 
that the hybrids are considerably 
more variable than either parent. 
At Mandan, N. Dak., in 1923, the 
threshed grain from 900 F 3 plant selec¬ 
tions was weighed and the yields are 
compared with those of the parents in 
Table XXV and shown graphically in 
Figure 8. 
Table XXIV.— Mean yield, standard deviation, and coefficient of variation for yield 
of plants of F ? hybrids, and of the parents Kota and Hard Federation varieties, 
grown at St. Paul, Minn., and Mandan, N. Dak., in 1922 
Station and material 
Mean 
yield 
Standard 
deviation 
Coefficient of 
variation 
ST. PAUL, MINN. 
Grams 
F 2 hybrid _ 
3. 97±0. 06 
2. 215±0. 045 
55. 793±1. 144 
Kota _ _ - _ 
6. 78± .34 
2. 129± . 239 
31. 401±3. 530 
Hard Federation_ 
1. 56±.. 16 
.966± . 115 
61. 923±7. 383 
MANDAN, N. DAK. 
F 2 hybrid _ _ 
4. 15± . 03 
1. 713± 0. 24 
41. 277± .579 
Kota _ 
3. 37± . 16 
1. 284± . 112 
38 101±3. 318 
Hard Federation__ 
1. 90db . 12 
1. 114± .082 
58. 632±4. 315 
and that at both points the coefficient of 
variation is greater for the hybrids 
than for Kota, the high-yielding parent. 
Because of the disparity of numbers 
of the parents and of the low mean yield 
of Hard Federation the standard devia- 
The data show that in segregation 
for yield the F 3 selections made in 1923 
were less variable, in comparison with 
the parent than were the F 2 selections. 
The mean yield, standard deviation, and 
coefficient of variation for the F 3 hy¬ 
brids and the parents are shown 
in Table XXVI. 
Table XXVI shows that the 
mean yield of the hybrids is 
slightly but not significantly 
less than that of Kota, the 
higher yielding parent, the dif¬ 
ference being 0.19±0.10 grams. 
The standard deviation and co¬ 
efficient of variation also are 
less than for Kota. The mean 
yield of a number of Marquis 
plants grown as checks was 3.03 
grams, which was slightly but 
not significantly less than the 
hybrid selections. 
As practically all the F 3 
plant rows were heterozygous 
for one or another of the plant 
characters studied, none of the 
rows was harvested for yield. 
As the mean yield of each 
selection was not obtained, it 
is not possible to show the 
segregation for yield in F 3 ac¬ 
cording to F 2 classes. 
Fig. 8.—Frequency distribution, by yield of plant, of F 3 
selections and of the Kota and Hard Federation parents at 
Mandan, N. Dak., in 1923 
