536 
Journal of Agricultural Research voi. xxiii, No. i 
Table X .—Correlation coefficients for protein in wheat and loaf volume 
Kind of wheat. 
Number of 
samples. 
Coefficients of 
correlation. 
Commercial varieties: 
North Dakota spring wheats. 
128 
— O. II72±0. 0588 
Minnesota spring wheats. 
202 
. 1827 ± . 0459 
Montana spring wheats. 
34 
•3555± • ion 
Colorado spring wheats. 
48 
. 4908 db .0739 
Montana winter wheats. 
91 
.3638^ .0613 
Ohio winter wheats. 
100 
. 5394 ± . 0479 
Minnesota winter wheats... 
43 
. 58741b .0674 
Kansas winter wheats. 
42 
. 7547 ± -0448 
Pure strains: 
Minnesota spring wheats. 
48 
. 4621± . 0766 
Wisconsin spring wheats. 
22 
. 5123db • 1061 
Maine spring wheats. 
3 i 
. 5 i 94 ± . 0885 
Ohio winter wheats. 
2 S 
• 5548 ± .0934 
The data in Tables IX and X, with the exception of those for North 
Dakota spring wheats and Minnesota commercial varieties of spring 
wheats, indicate a high, positive correlation. The coefficients of cor¬ 
relation range from — o. 1172 ±0.0588 for the North Dakota wheats to 
0.7547 ±0.0448 for the Kansas wheats. The negative correlation for 
the North Dakota wheats is not significant, since the value of the co¬ 
efficient is less than three times its probable error. The coefficient for 
the Minnesota commercial varieties of spring wheats indicates only a 
slight, positive correlation. This is rather of interest since both States 
are centers of production of the hard red spring wheat. In this connec¬ 
tion the observations of Thomas (14) may be cited which seem to throw 
some light on this point. Thomas found that high crude-protein con¬ 
tent as a rule is accompanied by high strength but that the relation 
between these two factors varies with different classes of wheat, and 
extremely high crude-protein—over 15 per cent—is sometimes accom¬ 
panied by a decrease in baking strength. The writer had occasion to 
observe several similar instances in pure lines selected from Preston 
wheats. Thomas further found that a wider variation in volume is 
noticeable with all classes of wheat for the lower percentages of protein 
than for the higher percentages, many samples with very high protein 
content being lower in strength than those having a medium content. 
In the light of these observations one may assume that the large number 
of samples with very high protein entering into the material from which 
the North Dakota and Minnesota data have been secured may have 
counteracted and neutralized the influence of the samples having a 
medium protein content. It should be noted, however, that the co¬ 
efficients for the Minnesota pure strains of spring wheat indicate a 
rather high positive correlation. 
PROTEIN IN PE OUR AND EOAF VOLUME 
The high correlation between the protein content in the wheat and 
protein content in flour points to a correlation between the protein 
content in flour and loaf volume which will closely agree with that 
between the protein content in wheat and loaf volume. 
