508 Journal of Agricultural Research voi. xxi, n«. 8 
Because of the assumed correlation between hardness and protein 
content, the commercial grading of wheat and the improvement of 
wheat by selection is based to a considerable extent on the hardness 
of the grain. The investigations reported in this paper had reference 
to improvement in the quality of wheat by selection. Since the pro¬ 
tein content of the grain is one of the chief factors that determine 
quality, the question which formed the central object of this investi¬ 
gation was whether a method of selecting for protein content could be 
devised that would not involve the necessity of making chemical analy¬ 
ses at first, where hundreds of strains or races of wheat are being tested. 
It is evident that, if hardness and protein content are genetically 
interdependent, this fact can be proved by means of the coefficient of 
correlation. It would not be possible, of course, to demonstrate the 
linkage of factors for any individual case. Likewise a parallel association 
of hardness and protein content might exist without any genetic relation¬ 
ship, so that a positive coefficient would not of itself prove such a 
relationship but would simply suggest the possibility of its presence. 
On the other hand, a negative coefficient would preclude such a 
supposition. 
For the purpose of the investigation, 94 pure strains of wheat, each 
the product of a single head, were chosen, and the correlation coefficient 
between hardness and the protein content was calculated. Hardness 
was expressed in terms of the crushing point. The method of determining 
the crushing point has been described elsewhere ( 3 ). 
For this determination 500 grains were used, it having been determined 
that this number gives accurate results. The analyses for protein were 
made by the department of chemistry of the Kansas Agricultural Experi¬ 
ment Station. The crushing points and percentages of protein are given 
in Table I 
TabliS I. —Crushing points and protein content of Q 4 pure strains of Kansas-grown 
wheat 
Serial No. 
Variety. 
909 
812 
8 95 
839 
6 59 
980 
89 I 
864 
865 
943 
871 
1117 
I37i 
ii43 
886 
Fuchs. 
Griechischer Sommer von Volo. 
Touzelle. 
Fenton. 
Blanc & duvet velout6. 
North Allerton. 
Duroselle. 
Jones Winter Fife. 
....do . 
Bastard.,. 
Urtoba. 
Turkey. 
U. S. Cereal Investigation No. 1656 
Japanese Velvet Chaff. 
Japhct. 
Crushing 
point. 
Protein 
content. 
Gm 
Per cent. 
3 , 9 ° 2 
57 
4, 260 
12. 24 
5 > 018 
r 5 - 5 2 
5 , 3 i 3 
11. 48 
5.407 
11. 68 
5 . 7°2 
10. 24 
6, 009 
10. 60 
6, 3°9 
12. 04 
6,319 
10. 96 
6, 328 
!• 36 
6, 340 
IO - 97 
6 , 401 
f 3 - 20 
6, 410 
10. 68 
6, 494 
10. 72 
0 , 516 
10. 48 
