14 BULLETIN" 916, U. S. DEPARTMENT OF AGRICULTURE. 



subjected to under commercial conditions. It is unfortunate that 

 lack of material prevented further tests on a commercial basis. How- 

 ever, enough evidence was obtained to justify the publication of the 

 results already obtained and to call the attention of growers and 

 shippers of potatoes to the facts here presented. 



SUMMARY. 



(1) Potatoes freeze more quickly when exposed to a rapidly dimin- 

 ishing temperature than when the temperature diminishes slowly. 



(2) Potatoes can be undercooled several degrees below their true 

 freezing point and then warmed again above the freezing point with- 

 out freezing injury, provided no ice formation takes place within 

 the tissue. 



(3) When undercooled, jarring resulting from rough handling or 

 incidental to hauling is liable to cause potatoes to freeze. 



(4) When undercooled in a temperature of 28° F., dropping from a 

 height of 2 feet caused potatoes to bruise badly and to show exten- 

 sive freezing injury. When dropped 1 foot they did not bruise, but 

 showed frost injury. When dropped 6, 4, or 2 inches once no injury 

 resulted, but when dropped six times frost injury followed. When 

 wet, injury also resulted. Potatoes supporting a 100-pound weight 

 were not injured. 



(5) When undercooled at 28° F. and rolled across the floor for a 

 distance of about 50 feet in bags freezing injury resulted. 



(6) When undercooled at 25° F. and dropped 6, 4, and 2 inches 

 once frost injury was apparent. 



(7) After freezing commences it is progressive. The amount of 

 injury caused within a stated time seems to depend upon the sur- 

 rounding temperature. 



(8) Immediately after inoculation the temperature of the potato 

 rises to its true freezing point and remains for a varying length of 

 time, depending upon the surrounding temperature. 



(9) Some varieties apparently are inoculated more easily than 

 others, even though their freezing point is higher. 



