Feb. 3, 1923 
Bacterial Leafspot of Geranium 
369 
P H values were found to vary from P H 7.0 to 6.6—that is, from neutrality 
slightly to the acid side. After inoculating, vigorous growth occurred in 
all cultures. At the end of 21 days tests were again made with the 
indicators. There was no increase in the hydrogen-ion concentration. 
As indicated by the records (P H 7.2 to 8.6) there was decrease in the 
hydrogen-ion concentration. In all five tests there was a uniformity of 
these changes in acidity, as shown by the indicators named above. 
The titrations with phenolphthalein of cultures grown in carbohydrate 
media containing Witte’s peptone were somewhat different from those 
made by Mr. Lewis with his organism, though not so strikingly so as 
with the Difco peptone. The second test was the only one that showed 
an increase in acidity throughout. 
At the time of Mr. Lewis’s experiments (his work was published in 
1914) Witte’s peptone was in general use in laboratory media. 
Table I .—Acidity of cultures of the writer’s geranium leafspot organism 
Medium. 
Ph. 
Fuller's scale. 
Witte's peptone. 
Difco peptone. 
Witte's peptone. 
Difco peptone. 
First 
test. 
Second 
test. 
Third 
test. 
Fourth 
test. 
Fifth 
test. 
First 
test. 
Second 
test. 
Third 
test. 
Fourth 
test. 
Fifth 
test. 
Saccharose: 
Uninoculated. 
7.0 
7.0 
7.0 
7.0 
6.8 
+8.5 
+9 
+10 
+ 10 
+13 
Inoculated 21 days.. 
7.6 
7-6 
7.2 
8.2 
7.2 
+12 
+17 
+15 
0 
+11 
Dextrose: 
Uninoculated. 
6.8 
6.7 
6.8 
6.8 
6.6 
+8.0 
+10 
+10 
+11 
+ 12 
Inoculated 21 days.. 
7.6 
7.8 
7-4 
7*4 
7-4 
+16.5 
+21 
+10 
+6 
+8 
Maltose: 
Uninoculated. 
6.9 
6.8 
6.8 
7.0 
6-6 
+8.5 
+9 
+9 
+ 11 
+ 12 
Inoculated 21 days.. 
8.2 
8.0 
7-4 
8.4 
7-4 
+4 
+ 16 
+ 7 
”5 
+8 
Lactose: 
Uninoculated. 
6.8 
6.8 
6.8 
7.0 
6.6 
+ 9-5 
+9 
+9 
+10 
+ 12 
Inoculated 21 days.. 
8.2 
7-6 
7-4 
8.6 
8.0 
+8 
+ 18 
+9 
—5 
+8 
Glycerine: 
Uninoculated. 
6.9 
7.0 
7.0 
7.0 
6.8 
+8.0 
+8 
+9 
+11 
+14 
Inoculated 21 days.. 
8.1 
7.6 
7-4 
7-6 
7*4 
+10.5 
+ 15 
+9 
+3 
+9 
Peptone water: 
Uninoculated. 
7-0 
No test. 
7-0 
7.0 
6.8 
+9.0 
No test. 
+9 
+9 
+ 12 
Inoculated 21 days.. 
8.1 
...do ... 
7-4 
8.4 
7-4 
+8 
...do ... 
+ 7 
5 
+8 
SENSITIVENESS TO ACIDS AND ALKALIES 
In uncorrected beef juice (titrating +23) part made alkaline with 
sodium hydroxid and part acidulated with hydrochloric acid the titration 
range of the organism is —6 to +28 (P H 8.7 to 5.7). 
Table I shows there is a reduction in the H-ion concentration after 
the organism has grown on the media 21 days when both Witte’s and 
Difco peptone are used. A reduction of acid is indicated on Fuller’s 
scale when Difco peptone is used, while with the Witte’s peptone there 
is no uniformity of reduction or increase of acidity (indicated on Fuller’s 
scale) though the table shows there are more cases of increase than 
decrease. 
The Lewis organism increased in acidity from 4 to 8 points on Fuller’s 
scale as Table II shows. 
