Aug. i, 1921 
Wound-Cork Formation in the Sweet Potato 
641 
A study of the influence of temperature upon cork formation was made 
after the potatoes had been in storage about 2 months. Halves of pota¬ 
toes from the storage house were placed in a series of chambers held at 
constant temperatures and humidities. Samples were taken whenever 
possible at intervals of 2 days for a period of 19 days. The potatoes at 
the higher temperatures soon decayed, so that in some cases only a few 
samples were obtained. Nevertheless, judging from previous work, it 
is thought that sufficient samples were available in every case for the 
purpose desired. In these tests all samples from each temperature were 
taken from the same half of the same potato and from a position just 
within the fibro-vascular ring. The temperatures and relative humidities 
at which these tests were carried out, as well as the results obtained, are 
shown in Table II. It is evident from this table that periderm formation 
was most rapid at a temperature of 33 0 C., cork production being evident 
in 4 days and pronounced in 8 days. The rate of cork development was 
about the same at 31 0 and 26°, producing in 11 days a layer about equal 
to that formed at 33 0 in 8 days. At 19.5 0 cork formation was greatly 
retarded, and at 11.2 0 no cork was formed by the fifteenth day, after 
which no examinations were made. Below this temperature no cork was 
formed within the time limit of this experiment (19 days). At 39 0 the 
potatoes decayed so rapidly that no samples were obtained after 4 days. 
In none of these samples was there any starchless layer formed. The 
walls of the cells just outside of the region where the cork layer probably 
would have developed if conditions had been favorable were usually 
somewhat thickened and suberized. The surface and subjacent cells 
were always dead and brown to a varying depth, depending upon the 
conditions of the environment. 
1 ABLE II .—Effect of temperature upon periderm formation 
This experiment shows that a protective cork layer will form at tem¬ 
peratures between 26° and 33 0 C., while below 26° the process is 
greatly retarded. As stated above, sweet potatoes are cured for from 
50936 0 —21- 3 
