10 
BULLETIN 916, U. S. DEPARTMENT OF AGRICULTURE. 
the blow caused by the fall. There was apparently no relation be- 
tween the weight of the potato and the freezing injur}^. In addition 
to the lots already described in this experiment, an additional lot of 
two of each variety was treated by striking each potato sharply with 
a pencil once, with the results shown in Table Y. It is difficult to 
state why it was necessary to drop the potatoes several times from 
2, 4, and 6 inch heights to produce frost injury, while one sharp blow 
with an ordinary pencil results in serious injury. The possible expla- 
nation is that the blow from the pencil caused a more violent concus- 
sion in a smaller area, from which the whole potato was inoculated. 
Table V. — Freezing injury to potatoes of seven different varieties undercooled 
at 28° F. and inoculated in different icays. 
Variety. 
Dropped 
2 inches. 
Dropped 
4 inches. 
Dropped 
6 inches. 
Struck with 
pencil. 
Check. 
In- 
jured. 
Unin- 
jured. 
In- 
jured. 
Unin- 
jured. 
In- 
jured. 
Unin- 
jured. 
In- 
jured. 
Unin- 
jured. 
In- 
jured. 
Unin- 
jured. 
3 
3 
1 
3 
3 
3 
3 


2 




3 
3 
3 
3 
3 
3 
2 






1 
3 
3 
2 
3 
3 
2 
2 


1 


1 
1 
1 
1 
1 
2 
2 
2 
2 
1 
1 
1 







1 


1 
3 
Irish Cobbler 
Spaulding No. 4 
American Giant 
Rural New Yorker. . 
Russet Rural 
Green Mountain 
3 
3 
2 
3 
3 
2 
Total 
19 
2 
20 
1 
IS 
3 
11 
3 
2 
19 
EXPERIMENT NO. 8. 
Two lots of one specimen of each variety of potato were held at 
28° F. for 24 hours, after which each potato of one lot was repeatedly 
bounced on the floor for about 10 seconds by dropping it from a height 
of not over 1 inch. After another 24-hour period all were removed. 
While none of the bounced specimens showed bruising or mechanical 
injury, they were all frost injured. The specimens of American Giant 
and Green Mountain froze solid, with resultant complete collapse on 
thawing. Of the check lot the Spaulding No. 4 and the Green Moun- 
tain varieties showed slight freezing injury. 
EXPERIMENT NO. 9. 
Lots of three potatoes of each variety were held at 25° F. for 18 
hours, after which they were dropped once from distances of 6, 4, and 
2 inches. After another hour all were removed. Examination 
showed that all dropped potatoes were injured, while in the check 
lot frost injury resulted to only one each of the Irish Cobbler, Ameri- 
can Giant, Kusset Rural, and Green Mountain varieties. 
Several experiments were conducted to test the rate at which the 
temperature of a potato will fall when exposed to a temperature be- 
low its freezing point. Figure 1 illustrates a typical set of results. 
