Dec. io, 1917 Breeding Sweet Corn Resistant to the Corn Earworm 567 
would appear to reduce damage more by reducing the number of larvae 
than by reducing the damage per larva, and it is difficult to imagine how 
a number of layers can have any direct effect on the number of larvae- 
unless the idea is entertained that a large number of closely wrapped 
layers causes the larvae to desert the ear. 
The relation between layers and number of larvae is not the result of 
any relation existing between layers and prolongation, since the partial 
correlation for constant prolongation is —0.47. The interprogeny re¬ 
gression of number of larvae on layers is 0.12—that is, the number of 
larvae is reduced on the average by 0.12 of a larva with the addition of 
each layer. 
The average intraprogeny correlation for these characters is —0.04, 
and the regression of larvae on layers is 0.01. 
In Table VIII the inter- and intra-progeny standard deviations, correla¬ 
tions, and regressions of the measures of injury and the more important 
protective characters are brought together for comparison. The uni¬ 
formly lower values of the intraprogeny regressions as compared with 
the interprogeny regressions support the idea that there are other import, 
ant characters not included among those recorded. 
Table; VIII.— Inter- and intra-progeny standard deviations, correlations, and regressions 
of the measures of injury and the more important protective characters of corn 
Factor. 
Stand¬ 
ard de¬ 
viations. 
Correlations. 
Regressions. 
Prolonga¬ 
tion. 
Number of 
layers. 
Husk 
leaves. 
Prolonga¬ 
tion. 
Number of 
layers. 
Husk 
leaves. 
Interprogeny. 
Mean intra- 
progeny. 
Interprogeny. 
Mean intra- 
progeny. 
Interprogeny. 
Mean intra¬ 
progeny. 
Interprogeny. 
Mean intra¬ 
progeny. 
1 
g 
£ 
Mean intra¬ 
progeny. 
Interprogeny. 
Mean intra¬ 
progeny. 
Interprogeny. 
Mean intra¬ 
progeny. 
Damage.per cent.. 
Number of larvae. 
Prolongation.cm.. 
3-74 
•23 
2.58 
i-13 
1. 20 
9 - 77 
.58 
3-48 
1.90 
2.01 
—0.71 
— .60 
—0.26 
— *13 
—0.52 
— . S i 
—0.10 
- *04 
0.31 
*52 
0.01 
•03 
1.02 
— *54 
—0.72 
— .02 
—1.72 
— . 12 
-0.51 
— .01 
0.97 
. 10 
0.05 
• ox 
Number of layers. 
Husk leaves.grades.. 
MATURITY 
A character often ascribed to sweet varieties is that they remain in 
an edible condition for a longer time than do field varieties. Compara¬ 
tively little damage is done after the ears have passed the edible stage, 
and, if the hardening of the grains was hastened, it seems not unreason¬ 
able that the injury should be diminished, and this might be a partial 
explanation of comparative immunity of field varieties. In the 1916 
experiments the majority of the ears were harvested between 16 and 
