552 
Journal of Agricultural Research 
Vol. XI, No. ii 
The 1915 planting was made at Chula Vista, near San Diego, Cal., on 
March 15. The corn earworm is a more serious pest in this region than 
at Lanham, Md., and a more uniform infestation resulted. 
In comparison with other plantings of sweet varieties in the same 
neighborhood, there seemed little doubt that the field of hybrids as a 
whole was less injured than other varieties. An effort was made, how¬ 
ever, to secure definite quantitative data on the effect of the selection, 
and to determine the characters most closely associated with immunity. 
The characters of the individual plants were recorded in a series of 
measurements described below: 
(1) Damage. —The portion of the ear rendered inedible was estimated on a scale 
of 10—that is, an ear in which the larvae had eaten completely to the base, rendering 
it worthless, was classed as 10. The slightest damage was recorded as 1 and an ear 
one-half of which was destroyed as 5. With intermediate stages estimated on the 
same scale, the grading was all done by the junior author and experiments showed 
that the maximum uncertainty regarding the class to which any particular ear should 
be referred was not greater than one grade. 
(2) Number op ear we. —The number of larvae found inside the husks at harvest, 
together with any which it could be seen had escaped. When the infestation is very 
severe, the fact that the larvae are cannibalistic would doubtless cause the recorded 
number to be lower than the true number. 
(3) Damage per earva. —The figure indicating the total damage of each progeny 
divided by the total number of larvae in the same progeny. 
(4) Proeongation. —The distance from the tip of the ear to the tip of the husks, 
recorded in centimeters. 
(5) Length op husks. —This measurement was obtained by adding the prolongation 
and length of ear. 
(6) Length op ear. —The length of the ear in centimeters, including any damaged 
portion. 
(7) Number op husks. —The total number of husks surrounding the ear. 
(8) Number op eayErs. —A small hole was cut through the husks at the side of the 
ear at a point about midway between the tip and the base, and the number of layers 
of husks at this point were recorded. 
(9) Days to sieking. — The number of days that elapsed from planting to the first 
appearance of silk. 
(10) Maturity. 1 — The degree of maturity was judged by slicing off the tops of the 
grains, and estimating the proportion of opaque to transparent endosperm. Prime 
eating condition was designated '‘ grade 10. ’ * The lowest grade that would be market¬ 
able on our scale would be about 6 and the highest about 15. 
(11) Sieking to harvest. 1 —The number of days’that elapsed between silking and 
harvesting of the ear. 
(12) Husk eeaves. —The extent to which husk leaves were developed was graded 
in accordance with an arbitrary scale ranging from o to 10. The same system of 
grading husk leaves has been used for a number of years in recording the behavior 
of all varieties grown and has proved to be a reliable measurement. 
(13) Number op rows. —The number of rows of grains on the ear was included in 
the notes largely as an indication of the circumference of the ear. 
Table II gives the mean value of each of the characters for each of the 
progenies grown in 1915. 
1 Not taken in 1915. 
