546 
Journal of Agricultural Research 
Vol. XXIII, No 7 
and furnish a larger loaf volume from a unit of flour than wheats with a 
low gluten content. The relationship is by no means perfect, probably 
because of the fact that a number of wheats with high gluten content 
fail to show good quality of gluten. In this connection it should be noted 
that the relationship between these two variables is to be studied for pure 
strains belonging to a given variety or group of wheat and considered 
within that group since there is some evidence indicating that certain 
wheat groups carry a larger number of varieties or strains of very high 
gluten content of poor quality than others. The durum and Preston 
wheats may be cited as illustrating this point. 
DISCUSSION OF RESULTS 
The relations considered in the preceding section will now briefly be 
considered from the standpoint of the plant breeder who desires to make 
use of any correlation between a wheat character determinable at an 
early stage of the pure line selection work and the baking strength of 
flour. 
Tables I to VI show data expressing the relationship between the crude 
protein in the wheat and its constituents, protein in flour, gluten, and 
gliadin. The correlations are very high and consistent, as would be 
expected. The correlation between crude protein content in the wheat 
and that ih flour is so high that, for practical purposes, the value for the 
protein content in the flour may be substituted for that in the wheat. 
This would eliminate the necessity of securing a sample of flour for 
analysis, which requires a larger amount of grain and an experimental 
mill to grind it, whereas for the determination of crude protein in the 
grain the yield of a single plant is sufficient. 
Of great interest are the correlations between loaf volume and the 
other chemical characters. The data given in Tables IX to XII indi¬ 
cate that the relation between loaf volume and crude protein in the wheat 
is paralleled by that between loaf volume and protein in the flour, the 
difference being one of degree as the relationship for the latter pair of 
characters is of greater intensity than that for the former. Since the 
correlation between loaf volume and protein in the flour parallels that 
between loaf volume and crude protein in the wheat, it would follow that, 
again for practical purposes, it may be sufficient to consider the crude 
protein in the wheat alone in relationship to strength of flour. 
Considering the gluten content and loaf volume, the data in Tables 
XIII and XIV, which are rather scant, indicate a very high, positive cor¬ 
relation between these two variables. Gliadin, which is one of the con¬ 
stituents of gluten and closely correlated with it (Tables XII and XXIII), 
generally bears a close relation to loaf volume (Table XXI). 
Finally, considering the quality of gluten and loaf volume, it will be 
seen from Tables XXVI and XXVII that loaf volume is more closely 
correlated with gluten quality than with any other character under con¬ 
sideration. 
From this brief consideration of the more important correlations it 
should be clear that as far as strength of flour is concerned gluten content 
and gluten quality show the highest degree of association with loaf volume. 
If these correlations are accepted as a working basis, the problem of find¬ 
ing a practical index of strength of flour is reduced to the task of deter¬ 
mining the gluten contend and gluten quality. In order to determine 
these two values a certain‘amount of flour is required. This is not avail- 
