634 
Journal of Agricultural Research 
Vol. XXI, No. 9 
The.se experiments show, then, that the cane sugar disappears when 
it is in combination with glucose, but that it is sparingly utilized when it 
is the only source of carbon. It has been shown that the growth of 
Rhizopus tritici renders the solution as well as the sweet potato more 
acid. In view of these facts it is probable that the increased acidity of 
both the decayed potato and the solutions is at least in part responsible 
for the inversion of the cane sugar. 
SUMMARY 
(1) The relative amount of C0 2 given off from the two halves of the 
same sweet potato, one of which was decayed with Rhizopus tritici , was 
determined. It was found that the decayed half gave off a total of from 
6.3 to 7.8 times as much C 0 2 as the healthy. Decay was completed in 
three days in all experiments except one which continued for one day 
longer. 
(2) At the close of the experiment the starch, cane sugar, and reducing 
sugar were determined in the healthy and decayed halves. There was a 
smaller amount of starch, cane sugar, and total sugars in the decayed 
sample than in the healthy one, while th e reducing sugars were increased 
in two experiments and decreased in two. 
(3) The total quantity of the carbohydrates (starch, cane sugar, and 
reducing sugars) lost in the decayed sample, according to calculations 
based on the analytical data, is greater than that lost through respira¬ 
tion, as measured by the C 0 2 given off. It seems, therefore, that a por¬ 
tion of the carbohydrates was utilized in other processes such as the 
production of fungous material, acids, alcohol, etc. 
(4) When the fungus was grown on cooked potatoes (sterile) a reduc¬ 
tion in the starch, cane sugar, and total sugar similar to that of the living 
potatoes took place. 
(5) In Czapek’s nutrient solution glucose was readily utilized when it 
was the only source of carbon available. When glucose and cane sugar 
were combined in the solution there was a reduction only in the amount 
of cane sugar. When cane sugar was the only available source of carbon 
it seemed not to be utilized by the fungus to any extent. 
LITERATURE CITED 
(1) Behrens, J. 
1898. bEitrage zur kenntnis der obstfaulnis. In Centbl. Bakt. [etc.], 
Abt. 2, Bd. 4, p. 514-522, 547 - 553 . 577 - 5 8 5 . 635-644, 700-706, 739- 
746, 770-777. Bibliographical footnotes. 
(2) Clark, W. Blair. 
1918. volumetric determination of reducing sugars, a simplification 
of scales' method for titrating the reduced copper without 
removing it from the residual copper solution. In Jour. Ainer. 
Chem. Soc., v. 40, no. 12, p. 1759-1772, 1 fig. 
