Aug. is, i 9 *8 Effect of Oxygen Pressures on Metabolism of Sweet Potato 283 
the absence of oxygen cane sugar is not formed in germinating peas and 
barley. Both of these investigators conclude that the presence of oxygen 
is one of the necessary conditions for the formation of cane sugar. 
This conclusion, however, is not of general validity, since the experi¬ 
ments with sweet potatoes show that cane sugar can be formed in some 
plant organs in the absence of oxygen. Possibly this difference in behav¬ 
ior of sweet potato roots and germinating seeds is associated with the 
difference in the degree of activity between dormant organs and active 
embryos or seedlings. 
From the correlation which he observed between the formation of cane 
sugar and aerobic respiration Boysen-Jensen believes that the respiratory 
process furnishes the energy necessary for the synthesis of cane sugar. 
If such a relation between respiratory energy and sugar synthesis exists 
it is not surprising that in some cases, as in the sweet potato, the requi¬ 
site energy can be derived also from the processes of anaerobic respira¬ 
tion. In such cases, however, we should expect to find the quantity of 
material consumed in anaerobic respiration greater than that consumed 
in normal respiration, since the energy derived from a given mass of 
material is not equal in the two cases. 
Two lots of halved sweet potatoes weighing, respectively, 1,273 and 
1,479 gm., were placed in respiration chambers at 30° C. Through the 
first chamber a rapid current of air was passed for three days and through 
the second a current of hydrogen was passed in the same manner. The 
daily carbon-dioxid output in grams per kilogram of the two lots of roots 
for the next five days was as follows: 
LOT I: POTATOES IN AIR. 
1.44 
I. 32 
I. 38 
I. 12 
I. OI 
LOT n: POTATOES IN HYDROGEN. 
I. 67 
I. 8l 
1. 85 
2. 03 
2.32 
On the hypothesis that in normal respiration glucose is completely 
oxidized to carbon dioxid and water, while in anaerobic respiration 
carbon dioxid and alcohol are formed, 1 gm. of carbon dioxid in normal 
respiration is equivalent to 0.682 gm. of glucose and in anaerobic respi¬ 
ration to 2.045 gm. of glucose. It is seen, therefore, that the quantity of 
material consumed in anaerobic respiration is actually much greater 
than that consumed in normal respiration. Moreover, in normal respi¬ 
ration the quantity of material consumed decreases as the plant adjusts 
itself to the conditions, while in anaerobic respiration the quantity in¬ 
creases. In a general way, therefore, the experiments reported in this 
paper and those reported in former papers seem to give some support 
to Boysen-Jensen's theory in so far as the production of cane sugar is 
greatest under conditions of greatest utilization of material by respi¬ 
ration. 
