512 
Journal of Agricultural Research 
Vol. V, No. ia 
the sweet potatoes when they were put into the incubator. Although 
there is a marked increase in both cane sugar and reducing sugar in 
the sweet potatoes, there is no evident general rise in the respiratory 
activity corresponding to the increase in the sugar content. During 
the course of the experiment the equivalent of 27.45 gm. of glucose 
was given off by the sweet potatoes as carbon dioxid, yet during this 
period 9.77 gm. of reducing sugar accumulated in them. The loss of 
weight of the sweet potatoes was 77 gm. 
Experiment 2.—The sweet potatoes used in the second experiment 
were of the same lot as those of the first, but they had stood in the 
laboratory at a temperature of about 20° C. until November 7. The 
weight of the roots used for the experiment was 3,029.8 gm. The loss 
of weight was 138.8 gm. The percentage of cane sugar rose slightly, 
but the reducing sugar fell from 2.21 to 1.18 per cent. The respira¬ 
tion was high at first and fell gradually, apparently with the decreas¬ 
ing percentage of reducing sugar. It is clear that if in this case the 
lowering of the respiratory activity is due to the decrease of sugar, the 
effect must be wholly attributed to the change in the invert-sugar con¬ 
tent, since the cane sugar, so far as may be judged from the analysis 
of the collateral sample, remained stationary or even rose slightly. The 
changes in the quantity of reducing sugar in these sweet potatoes are 
of special interest, for here the quantity of reducing sugar lost, accord¬ 
ing to calculations based on the analytical data, is greater than that 
lost through respiration as calculated from the quantity of carbon 
dioxid evolved. It seems, therefore, that a portion of the reducing 
sugar was used for other processes than respiration, possibly for the 
production of cane sugar. 
Experiment 3. —The sweet potatoes used in the third experiment 
had been subjected to the regular curing process and had thereafter 
been kept in cold storage at a temperature of 6° to 7 0 C. from Novem¬ 
ber 8 to December 9. The roots used in the experiment weighed 2,207.2 
gm., and their loss of weight was 184.2 gm. As a result of the expo¬ 
sure to low temperature, the sugar content of these sweet potatoes was 
higher than of those used in any of the other experiments. The respira¬ 
tion of these chilled roots was also very high, but sank rapidly toward 
the end of the experiment. The quantity of reducing sugar equivalent 
to the carbon dioxid evolved in respiration was greater than the appar¬ 
ent decrease calculated from the analytical data. 
Experiments 4, 5, 6 , and 7.—The remaining experiments all present 
a certain uniformity and may be described together. The sweet potatoes 
used in these experiments were cured in the usual manner and were 
thereafter stored at a temperature of 12 0 to 15 0 C., until the dates on 
which they were used. The weights of the sweet potatoes used in the 
different experiments were 1,984, 1,577.5, 1,898.5, and 1,054.5 gm., 
respectively. The corresponding losses were 143, 56.5, 59.3, and 40.8 
