416 
Journal of Agricultural Research 
Vol. XXVIII, No. 5 
three-fourths inch long, the tip of which is carefully squared to right angles 
with the axis. 
The instrument thus constructed is carefully standardized and a graduated 
scale reading in grams pressure equivalents placed upon the glass tube. The 
zero point is determined by the position of the indicator when the plunger comes 
to rest while hanging freely in a vertical position. Other points are determined 
by the position of the indicator when balancing the proper corresponding weights. 
The resistance of the kernels to puncture is determined by clear-cut positive 
readings, for when the pericarp is penetrated there is a sharp reaction of the 
spring. Definite measures of toughness of kernels on different parts of the ear 
are rapidly made. The instrument is easily operated by the right or left hand, 
as desired, and the ear of corn may be held either in the other hand or placed 
upon a table for the test. 
This instrument was in daily use throughout the season both in the laboratory and 
in the field, and its efficiency was found unimpaired at the conclusion of the work. 
Puncture tests were begun with the different varieties when the ears had 
reached the age of 10 days from the first appearance of silk and were made 
thereafter at 5-day intervals up to 30 days. From 3 to 5 representative ears 
were tested at each stage and 30 to 40 kernels on each ear, including those 
situated at the tip and butt as well as at the middle of the ear. The kernels 
tested were uniformly distributed over the whole ear though occasionally all 
the kernels of a single row were tested. The results of *an average test are 
illustrated by the following table, which shows the readings obtained upon 4 
ears of Howling Mob at the age of 15 days. The figures ^represent grams of 
pressure exerted by the needle of the instrument upon the kernels before the 
pericarp was penetrated. 
Table II .—Results of an average puncture test upon 4 ears of Howling Mob sweet 
corn at 15 days from date of first appearance of silks on these ears 
TFigures represent pressure in grams required before the needle penetrated the pericarp of the kernels. 
Date of test, July 27, 1922] 
First 
ear 
Second 
ear 
Third 
ear 
Fourth 
ear 
220 
215 
210 
200 
220 
235 
220 
180 
240 
205 
250 
180 
230 
185 
230 
220 
180 
195 
225 
245 
230 
230 
230 
220 
240 
175 
210 
200 
250 
230 
260 
195 
210 
225 
270 
195 
210 
225 
185 
160 
200 
220 
225 
200 
230 
240 
220 
190 
235 
215 
250 
210 
180 
175 
230 
190 
220 
195 
240 
210 
280 
260 
220 
180 
200 
255 
255 
220 
200 
240 
235 
210 
200 
210 
270 
205 
220 
225 
200 
220 
210 
185 
235 
205 
240 
220 
200 
195 
220 
210 
210 
200 
225 
210 
215 
180 
270 
210 
, 250 
180 
220 
230 
275 
230 
210 
230 
220 
195 
255 
180 
230 
235 
235 
205 
215 
205 
200 
195 
190 
180 
210 
_ | 
210 
190 
205 
Av.221 
214 
230 
201 
Grand average, 21G. 
