FACTORS EOR YIELD AND QUALITY OF SPRING WHEAT 
25 
In the present study the variability of the parent rows was in some 
cases greater than that of some of the hybrid strains. No sufficiently 
clear-cut differences in variability were obtained which could be 
used as a basis for separating the hybrids into homozygous early, 
homozygous late, or heterozygous groups. All of the hybrid plants 
labeled for date of heading are therefore combined, and the data, in 
comparison with the parents, are given in Table 25. 
The data show that the hybrids exceed the parents in variability 
and with a much wider range of variation in the Bozeman data than in 
those from Havre. It is very apparent that time is not the only 
factor concerned in bringing wheat from first to fully headed. Tem- 
perature, sunlight, moisture, and soil-fertility factors may be of 
equal importance. The number of days required for all rows at 
Bozeman, Moccasin, and Havre to pass from first to fully headed 
are shown in Table 26. 
Table 26. — Heading period in the F 3 generation of 672 Marquis-Hard Federation 
wheat hybrids, in comparison with 79 parent checks, grown at Bozeman, Moccasin, 
and Havre, Mont., in 1924 
Heading period (time from 
first to fully headed) 
Number of rows 
Bozeman 
Moccasin 
F 3 
hy- 
brids 
Hard 
Feder- 
ation 
Mar- 
quis 
F 3 Hard 
hy- Feder- 
brids I ation 
Mar- 
quis 
Havre 
F 3 j Hard 
hy- i Feder- 
brids ation 
Mar- 
quis 
3 days.. 
4 days.. 
5 days.. 
6 days.. 
7 days.. 
8 days.. 
9 days.. 
10 days. 
11 days. 
12 days. 
13 days. 
14 days. 
15 days. 
16 days. 
17 days. 
18 days. 
19 days. 
7 — 
1 
42 
1 
6 
59 i 
4 
2 
30 
3 
12 I 
1 
3 
1 
34 
13 
81 
2 
107 
12 
51 
6 
i 
17 
5 
Total - 
Average period in days. 
224 
11.4 
150 
6.0 
6.4 
5.1 
IS 
6.3 
17 
4.2 
The data show that there are numerous hybrid strains which head 
within a shorter period than the average of the parents. The later 
heading Marquis parent has a shorter average heading period than the 
early-heading Hard Federation parent at all three stations. The 
length of the heading period, for both parents and hybrids, decreases 
with increasingly unfavorable environmental conditions from Boze- 
man to Havre. 
Early heading was one of the objects for which these crosses were 
made. It is apparent that strains homozygous for relative date of 
heading were obtained by the F 3 generation and that some are 
nearly as early as the Hard Federation parent. 
79182— 26f 4 
