280 
Journal of Agricultural Research 
Vol. XIV, No. 7 
In experiments reported in previous papers it was found that an in¬ 
crease in reducing sugar precedes or accompanies the increase in cane 
sugar in the sweet potato. From these observations the conclusion was 
drawn that the monosaccharides result from the hydrolysis of starch, and 
that cane sugar is synthesized from these. The failure of reducing sugar 
to accumulate in an atmosphere containing only traces of oxygen might 
be attributed to two causes. First, to its more rapid utilization in the 
formation of cane sugar, and, second, to a greater demand for materials 
to sustain anaerobic respiration at the temperature at which the experi¬ 
ments were conducted. If, therefore, these processes, especially the 
respiration, could be retarded without retarding in a corresponding 
degree the hydrolysis of starch reducing sugar ought to accumulate in 
the absence of oxygen in the same manner as in air. To settle this 
point, a series of four experiments was carried out in which the potatoes 
were stored for different lengths of time from 3 to 20 days in hydrogen 
at a temperature of 4.5 0 C. 
Since, as has been stated, the hydrogen used in these experiments con¬ 
tained traces of oxygen and as no tendency toward the suppression of 
the formation of cane sugar was evident, it might be urged that the small 
traces of oxygen mixed with the hydrogen from the cylinders were suffi¬ 
cient to stimulate the processes leading to the formation of cane sugar. 
It therefore became necessary to exclude these traces in order to de¬ 
termine definitely whether cane sugar could be formed in the sweet 
potato in the absence of all traces of oxygen. For this purpose the 
hydrogen used in the last two experiments (Table IV, 10 and 20 days) 
was passed through a tube containing heated palladium asbestos. 
Analyses over mercury of the gas issuing from the chambers made on the 
day after the experiments were set up showed no oxygen present. 
The results of this series of experiments are given in Table IV. 
Table IV shows clearly the course of the carbohydrate changes in the 
absence of oxygen. After three days almost no change has taken place. 
After five days an increase in reducing sugar becomes apparent, but the 
increase in cane sugar is very slight. At the end of 10 days the reducing 
sugar has increased to from two to four times the original quantity, while 
the cane sugar still shows but very little increase. During the next 10 
days there is a further increase in reducing sugar, but this period is 
characterized mostly by the great increase in cane sugar. 
These facts show that the carbohydrate transformations in the sweet 
potato proceed in the same manner under anaerobic conditions as they 
do under aerobic conditions. The failure of reducing sugar to accumu¬ 
late at high temperatures under anaerobic conditions is probably in part 
attributable to its more extensive utilization in respiration. 
The data in the last two experiments (Table IV,*ro and 20 days) show 
that even in the entire absence of oxygen the formation of cane sugar is 
possible in the sweet potato. It is evident, therefore, that no significance 
need be attributed to the effects of the small traces of oxygen contained 
in the hydrogen used in the other experiments. 
