10 



BULLETIN 916, IT. S. DEPARTMENT OE AGRICULTURE. 



the blow caused by the fall. There was apparently no relation be- 

 tween the weight of the potato and the freezing injury. 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 ivays. 



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, Eusset 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. 



