532 
Journal of Agricultural Research 
Vol. XXVI, No. n 
and an increase in the carbon dioxid present in the storage air, these 
conditions were not responsible for the development of scald and, in fact, 
that increases in the carbon-dioxid content of the air actually tended 
to hold the disease in check. Experiments on humidity indicated that 
the benefits from air currents probably could not be attributed to their 
drying effect. Withered apples usually scalded less than crisp ones but 
apparently because of the aeration that accompanied the drying rather 
than from the drying itself. Apples stored in the air that was saturated 
with moisture but constantly stirred did not develop scald while similar 
apples in dry, stagnant air became badly scalded. The negative results 
along the above lines finally led to testing the effects of the odorous 
products of the apple. It was found that typical scald conditions, could 
be produced by exposing the apples to odorous substances similar to 
those given off by the apples and that various odor-absorbing materials 
such as fats and oils could be used as scald preventives. These facts 
gave the foundation for the development of the oiled wrapper. 
The data of the present paper furnish additional evidence in regard 
to the factors involved in scald control. That the question of humidity 
is secondary or negligible is indicated by the fact that the tin foil and 
glassine wrappers (see Table I) had little or no effect upon scald, by 
the fact that the paraffin wrappers had less than half the efficiency of 
the mineral oil wrappers, and also by the fact that the oiled and waxed 
apples although still oily and sticky at Ihe time of removal from storage 
were not protected from scald to anything like the degree that prevailed 
with the apples held in oiled wrappers. In these various tests there was 
apparently no correlation between moisture control and scald control. 
It was stated above that increases in the carbon-dioxid content of 
the storage air resulted in a decrease in apple scald. The oiled wrappers 
and the direct oil and wax treatments tend to restrict the free air move¬ 
ment between the apple tissues and the outside air and would favor 
the accumulation of the carbon-dioxid of respiration in the air within 
and immediately surrounding the apple. It would therefore seem possible 
that their value in scald control might be due to this restriction of gas¬ 
eous exchange. This can not be true, however, in so far as the direct 
physical protection of the oiled wrapper is concerned, for if this were 
the case the glassine wrapper, which is made of practically air-tight 
paper, should give better scald control than the oiled wrapper, the 
par affin wrapper should give practically as good control, and double 
and triple wrapped apples should have greater freedom from scald than 
single wrapped ones, all of which conditions are contrary to the facts. 
If the oiled wrapper is of value on account of physical barriers set up, 
it must be through the coating of oil it deposits on the apple. 
With the oil and wax treatments of the apple and with the film of oil 
that passes over from the wrapper to the apple there is the possibility 
both of restriction in gaseous exchange and of more direct physiological 
effects upon the skin of the apple. That a definite physiological effect 
is produced is evidenced by the fact that the development of yellow 
in the ground color of the apple is delayed by both methods of treatment 
and approximately in proportion to the amount of oil that is deposited 
on the apple. It would seem probable that any agency that had a check¬ 
ing or inhibiting effect upon the skin of the apple might at the same 
time be responsible for a reduction in scald, but it does not seem possible 
to fully explain the scald control secured with the oiled wrapper on this 
