Aug. i, 1921 
Wound-Cork Formation in the Sweet Potato 
639 
held in moist chambers healed in a normal manner, while corresponding 
halves kept on the desk beside the moist chamber showed only a drying 
and death of the surface several cells in depth. It is not known why the 
cork layer failed to form in the latter case. However, it may possibly be 
due to insufficient transpiration or to the lack of oxygen. The dry and 
hard surface layer no doubt serves to check the interchange of moisture and 
ox}^gen between the underlying cells and the outside air. Kiister (8) says 
in this connection that at least a small degree of transpiration must be 
possible for the exposed tissue, while he, as well as others (6, 10, 7, /j), 
regards oxygen as a determining factor. Some attention has been given 
by the writers to the progress of healing under storage-house conditions. 
Experiments were conducted to show whether cork was formed under 
storage conditions and, if so, what effect the temperature maintained in 
the house at the time the potatoes were placed in storage might play. 
It is generally recommended that the storage house be kept at a tempera¬ 
ture of 25 0 to 30° C. during the digging period and for 10 to 15 days there¬ 
after. Sometimes no attempt is made to raise the temperature to that 
height until after the potatoes are all dug. This may mean the lapse of a 
week or more before the curing period starts. 
A quantity of sweet potatoes were taken from the held to the storage 
house, cut into two parts longitudinally, and samples taken each day for 
six days. These showed a dying of the cells for a considerable depth 
beneath the wounded surface but no differentiation of a starch layer and 
no cork formation. In another experiment the potatoes were cut on 
the day the curing period began. Here again there was no differentia¬ 
tion of a starch or a cork layer but a dying of the exposed cells, which 
formed a hard covering over the wounded surface. No doubt either the 
temperature or the humidity or both were not such as to permit the 
normal healing process to take place. 
The potatoes used in both of these experiments showed no signs 
of decay in the two weeks during which they were under observation. 
The dried surface of the wound seemed to afford an efficient barrier to 
infection. In order to test further the ability of a dried surface to pre¬ 
vent infection the following experiments were conducted. 
Potatoes were taken directly from the field and placed in a dryer de¬ 
signed primarily for desiccating sweet potatoes and other vegetables. 
The potatoes were spread out thin over a wire netting, and a current of 
warm air was forced up among them. The quantity of potatoes used, 
together with the air temperature and rate of air movement, is given in 
Table I. The potatoes after being treated were kept in the drying room 
in crates until the curing period was over, after which they were moved 
to the sweet-potato storage house. Observations on the keeping quali¬ 
ties of these potatoes were made from time to time, and samples were 
taken for the study of the cork formation. The table shows also the 
