FACTORS FOR YIELD AND QUALITY OF SPRING WHEAT 
21 
The data do not show large early and small late groups but indicate 
that early heading is partially dominant, as the mean date of heading 
of the hybrids was nearer that of the early Hard Federation parent. 
The reciprocal crosses show slight maternal influence, with a differ- 
ence of 0.97 ±0.11 days in mean date of heading. Statistically this 
difference, which is 8.8 times its probable error, is significant, as is 
also the difference of the mean of each reciprocal cross from the mean 
of the total F 2 population. 
The variability of the hybrids is much greater than that of either 
of the parents. The extreme dates for earliness or lateness in both 
parents, however, were not reached by any of the F 2 plants. Varia- 
bility constants, determined by computing the vegetative period, or 
days from emergence to heading, for the parents and the hybrid 
material are given in Table 21. 
Table 21. — Mean, standard deviation, and coefficient of variation for the vegetative 
period, or days from emergence to heading, of F 2 hybrids and for the Hard Federa- 
tion and Marquis parents grown at Bozeman, Mont., in 1928 
Material compared 
Mean (days) 
Standard 
deviation 
Coefficient 
of variation 
F2 hybrid... ... .. 
45. 79±0. 05 
43.29± .09 
51. 52± . 12 
1. 956±0. 039 
1.373± .066 
1.819± .087 
4. 272±0. 084 
Hard Federation 
3. 172± . 152 
Marquis.. . . -...-. 
3.531± .168 
The data show that the F 2 hybrids are much more variable than 
either parent. The differences in the coefficient of variation of the ¥ 2 
hybrids and that of Marquis, the most variable parent, is 0.741 ± 
0.188, which difference, being 3.9 times its probable error, indicates 
odds of over 116 to 1 that the occurrence 01 such variation was not 
due to chance alone. 
Table 22. — Dates of first heading in the F 3 generation of 674 Marquis-Hard Federa- 
tion wheat hybrids, in comparison with 79 parent checks, grown in nursery rows 
at Bozeman, Moccasin, and Havre, Mont., in 1924 
Number of rows 
Dates of first heading 
Bozeman 
Moccasin 
Havre 
F 3 
hybrids 
Hard 
Feder- 
ation 
Mar- 
quis 
F 3 
hybrids 
Hard 
Feder- 
ation 
Mar- 
quis 
F 3 
hybrids 
Hard 
Feder- 
ation 
Mar- 
quis 
July 2 
2 
9 
22 
26 
28 
37 
24 
2 
4 
5 
July 3 
2 
39 
66 
56 
39 
17 
3 
1 
1 
5 
7 
1 
July 4 
July 5 
July 6 
5 
15 
40 
74 
102 
28 
23 
11 
2 
July 7.... 
2 
3 
1 
7 
8 
10 
July 8 
July 9 
5 
4 
July 10 
July 11 
1 
July 12 
6 
July 13 
10 
July 14 
1 
Total 
224 
13 
3.7 
13 
9.0 
150 
5.9 
9 
2.6 
9 
9.4 
300 
9.7 
18 
7.6 
17 
Average date, July 
5.7 
12.7 
