12 



BULLETIN 916, TJ. S. DEPARTMENT OE AGRICULTURE. 



The temperature of the air surrounding the potato at the time freez- 

 ing took place rose from 25.6° to 26.6° F., due to heat liberated by the 

 potato. 



SUMMARY OF RESULTS OBTAINED BY DROPPING UNDERCOOLED POTATOES. 



When undercooled at 28° F. and dropped 4 feet and 2 feet, the 

 potatoes were severely bruised and showed extreme freezing injury 

 of the vascular type. When dropped 1 foot, no bruising resulted, but 

 all varieties froze except the Green Mountain and Spaulding No. 4. 

 The type of injury was a faint blotch. When dropped 6, 4, and 2 

 inches once, no freezing injury resulted ; but when dropped six times 

 from these heights, severe injury followed. When bounced several 

 times by dropping 1 inch, severe injury followed; in some cases the 

 potatoes were frozen solid. When undercooled at 25° F., dropping 

 once from 6, 4, and 2 inches caused injury. 



Some further experiments were undertaken to determine what 

 other forms of disturbances will inoculate undercooled potatoes. 

 Duplicate lots of 12 specimens each of the Eural New Yorker variety 

 were placed at 25° and 28° F. for 24 hours. At each temperature 

 one lot was placed in the direct draft from an electric fan, while the 

 other lot was protected from the draft to act as a check. At 25° F. 

 10 of the 12 potatoes in the draft showed injury; also 3 of the 

 check lot were injured. At 28° F. no injury was found in either lot. 

 A possible explanation for the fact that the potatoes froze when 

 exposed at 25° F. to a strong current of air is that they undercooled 

 much more rapidly than the lot not in the draft. 



Two lots of six specimens each of Rural New Yorker were held at 

 28° F. for 24 hours, then wet and removed after another 24 hours. 

 All of the lot that were wet were injured, while three of the lot that 

 were not wet also were injured. In the next experiment two lots 

 consisting of two of each variety were held at 28° F. for 24 hours ; 

 they were then wet and held for another 24 hours. The results ob- 

 tained on examination are shown in Table VI. 



Table VI. — Freezing injury to potatoes of seven different varieties held at 

 28° F. for 24 hours and then wet while undercooled. 



Variety. 



Wet. 



Cheek. 



Injured. 



Uninjured. 



Injured. 



Uninjured. 



Triumph 



2 

 2 

 

 1 



2 

 2 

 1 



<<0 





 2 

 1 

 

 



1 





 

 

 

 1 

 

 



2 





2 





2 





2 





1 





2 





2 







Total 



10 



4 



1 



13 







a Faint blotch. 



