136 
Journal of Argicullural Research 
Vol. XXI, No. a 
Since none of the cultures of the tomato organism showed any change 
toward the yellow color, it is evident that in no case was there any increase 
in the hydrogen-ion concentration. On the contrary, as indicated by 
the phenol red, there was a decrease in the hydrogen-ion concentration 
to some point in the neighborhood of P H 8. This decrease occurred 
most rapidly in the lactose cultures. 
That this failure to produce acid was not due to the possible masking 
effect of the alkaline products of peptone digestion was proved by the 
fact that in a bouillon culture containing 5 per cent peptone there was 
after 3 days’ incubation no decrease of the hydrogen-ion concentration as 
indicated with phenol red. 
Agar with sugars. —Abundant growth occurred in slant cultures on 
litmus dextrose, litmus maltose, and litmus lactose agar. There was no 
change in the litmus lactose agar until after 20 days, when the color 
became more bluish. In the other two media the litmus was entirely 
faded at the end of 10 days because of reduction, but a pale blue color 
returned at 20 days similar to that in the lactose agar. No pink color 
was produced at any time. This indicates that there was no increase 
in acidity. A pink color was produced in a parallel series of Bacillus 
colt cultures. 
To check up the test with litmus, a similar test was run in a triple series 
with the three sulphone-phthalein indicators described above—that is, 
brom cresol purple, brom thymol blue, and phenol red. These media 
were adjusted to a reaction very close to true neutrality or P H 7 as indi¬ 
cated by the grass-green color of the brom thymol blue and the yellow 
color of the phenol red. Abundant growth occurred. While the Bacil¬ 
lus coli cultures became distinctly yellow, there was no marked change 
in the other cultures. The phenol red assumed a more distinct red 
than the controls. The brom thymol blue in the dextrose agar and the 
brom cresol purple in the dextrose and maltose agars faded slightly. 
With the tomato organism, therefore, no increase in acidity occurred in 
these sugar agars. 
Action on starch. —In plates of beef agar to which potato starch 
was added, halos 3 to 6 mm. in width appeared about the colonies from 
loop plantings at the end of 5 days. When a,solution of iodin in potas¬ 
sium iodid was added, the clear zones under and around each colony 
proved that the starch had been destroyed therein. In similar plate 
cultures on agar containing corn starch, clear halos were also visible 
when the iodin test was applied. There was, therefore, vigorous diastatic 
action on potato and corn starch by an enzym which diffused out into 
the agar. 
The cooked potato tissue used as a culture medium was tested with 
iodin. Microscopic examination showed that the tissue disintegrated 
by the growth of the organism gave no blue color, even within the cells, 
while in the uninoculated tissue a deep blue color developed. In the 
