Aug. i, 192X Changes Caused in Sweet Potatoes by Rhizopus tritici 633 
were utilized largely in supporting an energetic respiration and in the 
construction of fungous material. In the second experiment with a 
smaller amount of fungous growth a correspondingly less amount of 
sugar would be utilized in supporting respiration and in the construction 
of fungous material. The conversion of the cane sugar and starch into 
reducing sugars probably took place faster than it was utilized; hence 
its accumulation. 
Further interesting facts as regards the availability of monosac- 
cliarids and disaccharids in supporting the growth of this fungus are 
shown by experiments in which cane sugar and glucose alone and in 
combination are used as the only sources of carbon in Czapek’s nutrient 
solution. 
In nutrient solutions. —For each experiment three flasks were 
prepared to contain a modification (10) of Czapek’s nutrient solution 
and 1 per cent of glucose and cane sugar alone and in combination as 
the only source of carbon. The solutions were then inoculated, and the 
fungus was allowed to grow for 17 days. At the end of the growth 
period the mycelium was removed and the dry weight of fungous mate¬ 
rial determined. The reducing sugars and cane sugar were again deter¬ 
mined. The loss of glucose and cane sugar as well as the dry weight 
of the fungous growth are shown in Table IV. 
Table IV. —Loss of glucose and cane sugar and amount of fungous material produced 
Experi¬ 
ment No. 
Carbohydrates present. 
Loss of 
dextrose .' 1 
Loss of 
cane sugar, a 
Dry weight 
of fungous 
material. 
[Glucose. 
5 2 -347 
O 
Gm. 
O. 3954 
640 
Glucose and cane sugar. 
Cane sugar. 
[Glucose. 
O 
O 
57-99 
60. 68 
12.Il8 
O 
- 3583 
• 2430 
• 5 TI 3 
656 
< Glucose and cane sugar. 
[Cane sugar.. 
0 
63-38 
Co. 09 
O 
O 
•5158 
• 0853 
■ 5 2 53 
669 
| Glucose and cane sugar. 
[Cane sugar.. . 
4 . 53 
0 
59 - 49 
5 - 7 i 3 
. 5060 
• I 5 I 4 
a Expressed in milligrams per io cc. of solution. 
The results of these experiments show that when cane sugar is the 
only source of carbon a small amount of fungous material is produced. 
In experiment 656 there was no loss of cane sugar, and in each of the 
others the loss was slight. These results would seem to indicate that 
cane sugar when present alone in the solution is not readily utilized. 
On the other hand, when cane sugar and glucose are added together in the 
solution in equal amount, the loss of the former is relatively large but the 
latter remains practically constant. When, however, glucose is the 
only source of carbon there is a considerable reduction in the amount 
present at the end of the experiment. 
