4 BULLETIN 916, U. S. DEPARTMENT OF AGEICLTLTUEE. 
posed to a temperature of 8.7° froze in 6 minutes when the actual 
internal temperature had reached 23° F. The other potato was 
exposed to 15.8° and froze in 12.5 minutes when the internal tem- 
perature had reached 20.2° F. The actual freezing point of both 
potatoes was 29.15° F. This substantiates the results obtained by- 
Jones. Miller, and Bailey (4) . They cite an instance of a tuber freez- 
ing in 80 minutes when undercooked to 24.44°, while another exposed 
to a slowly diminishing temperature did not freeze until 13.1° F. 
was reached. Another specimen froze in 40 minutes when under- 
cooled to 26.4° while exposed to a rapidly diminishing tempera- 
ture which had reached 12.2° F. They state that, in general, po- 
tatoes do not freeze until exposed to 26.6° F. or lower. To judge 
from the results submitted in this report it is possibly safe to state 
that except in the case of accidental inoculation the degree of under- 
cooling at which freezing occurs depends upon the variety, the 
rapidity with which undercooling progresses, and the length of ex- 
posure to a given degree of undercooling. 
PLAN OF THE WORK. 
In order to apply to the handling of potatoes the knowledge of the 
process of undercooling and freezing already gained, a series of ex- 
periments was conducted at the Arlington cold-storage plant of the 
Bureau of Plant Industry. It has been noted by potato growers and 
shippers that sometimes one lot of potatoes while being handled or 
otherwise disturbed in transit will freeze when another left undis- 
turbed at the same temperature remained uninjured. Some apple 
handlers are very careful not to jar or jolt frosted apples, because 
they say it will cause them to bruise and rot. It is a practice among 
some onion growers to store their onions through very severe winter 
weather in mows or buildings between layers of hay where they are 
undisturbed during the winter. These persons will often guard 
against loose doors or shutters which can be slammed by the wind, 
as this is liable to cause the onions to freeze and subsequently to rot. 
Xumerous instances are reported where potatoes have been exposed 
for hours or even days to temperatures below their freezing point 
without injury. Muller-Thurgau reported having stored potatoes 
at 32° to 26.6° F. for two weeks without injury. Of course, internal 
frost injury may have been present without its being detected unless 
the potatoes were cut open and examined. 
In the present work seven standard varieties of potatoes, all true 
to name and grown under the same conditions by the Bureau of 
Plant Industry at the Aroostook Farm of the Maine Agricultural 
Experiment Station, were used. These varieties were the Triumph, 
Irish Cobbler, Spaulding Xo. 4. American Giant. Rural Xew Yorker, 
