512 Journal of Agricultural Research voi. v. no. 12 



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 g^i- 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° 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° to 15° 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 



