20 
BULLETIN 1403, U. S. DEPARTMENT OF AGRICULTURE 
sacrifice of yield. The importance of a study of the effect of maturity 
under the three different Montana conditions is apparent. This 
study has been made from the dates of heading, dates of ripening, 
and the days between these dates or from the heading, ripening, and 
fruiting periods. 
The heading period usually is least affected by environmental 
conditions, and the senior writer {5) has thought that it is the best 
measure to use in a study of maturity inheritance. 
Farrer (7) found that the heading period in F t hybrids is inter- 
mediate to those of the parents and that there was no difference in 
this respect in reciprocal crosses. Bryan and Pressley (3), in crosses 
between Sonora and Turkey, found the F t intermediate in time of 
heading to the parents and the F 3 majority inclined toward the late 
parent. Clark (5) in KotaxHard Federation and reciprocal 
crosses found in F 2 studies at three points that earliness, as deter- 
mined by date of heading, is dominant to lateness and that there 
were slight but significant differences in reciprocal crosses. Florell 
(.9), from F 2 results with Sunset-Marquis crosses, also concluded that 
early heading is dominant and found that "there was a distinct 
heaping up of the population into a large early and a small late group 
in the proportion of 3.07 to 0.93." 
In the present study, comparisons of dates of heading of the Ft 
generation with parents are not available, but F 2 data from reciprocal 
crosses grown at Bozeman in 1923 with those from parent plants 
are presented in Table 20 and are shown graphically in Figure 1. 
All dwarf plants were omitted from this study. The dates of heading 
were obtained by tagging the plants individually on the day the first 
head emerged from the sheath. 
Table 20. — Segregation in the F 2 generation into daily frequency classes for date 
of heading of 583 plants of MarquisXHard Federation and reciprocal wheat 
crosses, in comparison with the parents, grown at Bozeman, Mont., in 1923 
Number of plants 
Dates of heading 
F2 hybrid 
Hard 
Federation 
Hard 
Federation X 
Marquis 
Marquis X 
Hard 
Federation 
Total 
Marquis 
July 12 
9 
July 13. 
10 
33 
63 
64 
61 
31 
8 
9 
I 
3 
2 
2 
13 
35 
45 
76 
60 
37 
12 
9 
1 
2 
12 
18 
July 14 
46 38 
98 1 8 
109 ! 23 
137 1 
91 1 2 
45 1 
21 f 
12 
July 15. 
July 16-- 
July 17 
July 18 
July 19 
July 20. 
1 
July 21 
11 
July 22 
3 
5 
19 
July 23. 
26 
July 24. 
2 .. 
13 
July 25 
1 
1 
1 
1 
19 
Julv 26. 
4 
July27 
4 
July 28 
1 
July 29 
2 
Total 
Mean and probable error 1 
289 
16. 30±0. 08 
294 
17. 27±0. 07 
583 99 
16.79±0.05 1 14.29±0.09 
100 
23. 52±0. 12 
1 It is recognized that a date is a unit, but for averages it seems necessary to use fractional dates in order to 
:how accurate differences in time of heading and ripening. 
