FACTORS FOE YIELD AND QUALITY OF SPRING WHEAT 33 
which ripen in a shorter number of days than the average period of 
the parents. The earlier ripening Hard Federation parent ripened 
in a shorter period than the later ripening Marquis parent at two of 
the three stations. Among the check rows of parents the variation 
in days from first to fully ripe is less at two of the three stations than 
the average ripening period. In general, about half of the F 3 hybrid 
families ripened in a period equal to or less than the average of the 
parents. It is not possible to separate the hybrid material with suffi- 
cient accuracy, however, to make a genetic interpretation. 
Late ripening was one of the objects for which these studies were 
made, and from a breeding standpoint it is apparent that homozy- 
gous strains for the ripening period have been obtained by the F 3 
generation and that some strains are as late or later ripening than 
the late Marquis parent. 
FRUITING PERIOD 
The term " fruiting period" as a designation for the number of 
days from heading to ripening was first used by Carleton (4-, p- $75) 
in 1905. He later emphasized its importance "as the most critica] 
period in the life of the crop" and called attention to "the correla- 
tions existing between the length of this period and certain other 
characteristics of the crop, as yield and protein content." 
As early as 1893 Schindler (16) had observed that — 
With the length of the vegetative period, especially in respect to the length 
of the interval between flowering and ripening, not only does the dimension of 
the kernel increase but the amount of carbohydrates stored therein increases 
and the protein content decreases. 
Thatcher (18, pp. 39-4-7) and his students studied this problem 
with plants from four varieties and found that the average weight of 
kernel varies directly and the percentage of nitrogen inversely with 
the length of the fruiting period. 
Since 1915, among other data, the length of the fruiting period has 
been recorded (C. I. form No. 13) in all varietal experiments con- 
ducted by the Office of Cereal Investigations. During the first three 
years, 1920 to 1922, inclusive, that Hard Federation was included in 
the varietal experiments at Moccasin, it outyielded Marquis by an 
average of 6.2 bushels per acre. R. W. May, assistant agronomist, 
in charge of the experiments, noted that each year the higher yield 
of Hard Federation was associated with a longer fruiting period. 
During these three years the average fruiting period of Marquis was 
29 days and that of Hard Federation 37 days, a difference of 8 days. 
The results with these two varieties appeared to be an outstanding 
instance of the probable positive correlation of the relative length of 
fruiting period with yield. The present study, accordingly, was 
outlined partly to determine the inheritance of modification in length 
of the fruiting period, but more particularly to determine its inter- 
relationships with the heading period and the ripening period and 
its importance from a breeding standpoint in affecting the yield and 
crude-protein content of hybrid strains. 
No comparison of the fruiting periods of the F t hybrids with 
those of the parents was attempted. The F 2 data obtained are not 
comparable with those of the Marquis parent, because of the con- 
fusion in the seeding plans previously mentioned. The fruiting 
79182—26J 5 
