Mar., 1923] WEIMER AND HARTER — PECTINASE PRODUCTION 131 
at the intermediate temperatures or in the vicinity of 20° C. Since this 
temperature is favorable for decay, it may be assumed that, within rather 
wide limits, the amount of pectinase produced is greatest at the temperature 
most suitable for the decay of sweet potatoes. 
Maceration of Old and New Potatoes 
Some of these investigations were conducted during the summer and 
autumn months, when either old sweet potatoes kept from the preceding 
crop or immature potatoes taken from the ground had to be used. The 
question naturally arose whether the old and the new potatoes would be 
macerated at the same rate. 
It is believed by some investigators that sweet potatoes which have 
been in storage for some time are more readily decayed than those freshly 
dug, and there is some evidence which indicates that such is the case. The 
writers therefore decided to carry out a series of experiments to determine 
if there is any difference in the rate at which the middle lamellae of stored 
and freshly dug potatoes are dissolved. The experiments were conducted 
according to the method already described with all the species of Rhizopus, 
the organisms having been grown at 40°, 30°, and 9 0 C. and maceration 
carried out at 40°. At 40° and 30° the organisms were grown for 3 days, 
at 9 0 for 26 days. The old potatoes had been in storage for about 10 
months. The new potatoes were freshly dug or had been in storage for 
only a few weeks at most. 
The results of these investigations are shown in table 2. 
Table 2. Comparative rate of maceration of old find new potatoes* 
Solution 
Temperature 
for Growth of 
Fungi (° C.) 
Kind of 
Potatoes 
R . 
re- 
flexus 
R . 
dele- 
mar 
R . 
oryzae 
R . 
chi¬ 
nensis 
R . 
nodo- 
sus 
R . 
tritici 
R . 
micro- 
sporus 
R . 
may- 
dis 
R . 
nigri¬ 
cans 
40. 
30. 
9. 
Old. 
New. 
Old. 
New. 
Old. 
10 
12 
2-75 
4-5 
2.5 
3 
4-7 
5.25 
2.1 
4-25 
4- 7 
5- 5 
2.15 
4-5 
3.25 
5 
4-9 
12 
4-5 
6 
3-25 
3- 75 
2.05 
4- 25 
1.87 
2.4 
4 
4-5 
1- 45 
2- 75 
2 
2.5 
24 + 
48 + 
5-5 
7 
i-3 
2 • 
48 + 
48 + 
New. 
Mycelium 
40. 
Old. 
8 
7 
5 
575 
8 
7 
3-8 
5-25 
2.5 
4 
8-24 
14 
6 
14 
4 
3-5 
3-8 
5 
2.87 
4 
4-5 
4-5 
2- 5 
3- 25 
2.67 
4 
. 
^0. 
New. 
Old. 
3 
3.25 
2.75 
4 
. 
9. 
New. 
Old. 
24 
48 + 
24 
48 + 
New. 
* Figures indicate time in hours necessary to complete maceration. 
The results show that in nearly all cases the old potatoes are more 
readily macerated than the new. In some instances, for example, chinensis , 
