274 
Journal of Agricultural Research 
Vol. XIV, No. 7 
in germinating barley and peas under similar conditions. With this 
idea in view a study of the effects of different oxygen pressures on the 
carbohydrate transformation in the sweet potato was undertaken. 
EXPERIMENTAL METHODS 
The general method adopted was that heretofore used of cutting sweet 
potatoes into halves lengthwise and storing one half under experimental 
conditions, while the other half was prepared for immediate analysis. 
The potatoes were always dug in the afternoon, properly cleaned, and 
stored in a cool place until the following day, when they were prepared 
for the experiments. Either five or six individuals were used for each 
experiment. 
With respect to the total gas pressure to which the stored halves were 
subjected, the experiments may be divided into three groups: (i) experi¬ 
ments at pressures greater than one atmosphere; (2) experiments at 
atmospheric pressure; and (3) one experiment at a pressure of less than 
one atmosphere. 
In the experiments at pressures greater than one atmosphere the 
potatoes were stored in a gas-tight iron cylinder 33 cm. high and 22.9 
cm. in diameter. The pressures were measured by means of a standard 
test gauge in the head of the cylinder. The whole apparatus, except 
the projecting gauge, was submerged in a constant temperature water 
bath. Preliminary experiments showed that with an inside pressure 
of 10 atmospheres there was no leakage from the cylinder during a period 
of 10 days. 
In the second group of experiments the potatoes were stored in oxygen, 
air, or hydrogen at atmospheric pressure. For this purpose desiccators 
kept in constant temperature chambers were used. For the experiments 
in air the desiccators were merely ventilated, but in the other experi¬ 
ments the gases were passed through the desiccators in a rapid stream 
until all the air had been replaced. Thereupon the current was slowed 
down until 60 to 100 bubbles of gas per minute passed through wash 
bottles at the exits. Before entering the desiccators the gases passed 
through about 10 meters of copper tubing coiled in the constant tempera¬ 
ture chambers and then through wash bottles filled with water. Short 
thermometers placed in these wash bottles showed that the gases entered 
the desiccators at the temperature of the chambers. The oxygen and 
hydrogen were obtained from cylinders furnished by a commercial 
company. The hydrogen contained approximately 0.17 to 0.25 per cent 
of oxygen. In two experiments, as will be mentioned later, these small 
traces of oxygen were removed from the hydrogen. 
The single experiment in which the potatoes were stored at less than 
atmospheric pressure was carried out by means of the gas cylinder 
described above. 
