A Bacterial Disease of Alfalfa 
19 
TABLE NO. 4—RELATION TO ALKALI. 
7. Optimum Reaction. 
The optimum reaction for growth in bouillon is +15° to +18° 
Fuller’s scale. 
8. Vitality on Culture Media. 
Vitality on culture media is only moderate. Transfers made 
from a stab culture in nutrient agar which was four months old 
failed to give any growth; however, growth has been obtained 
from cultures on agar which were six weeks old. No difficulty 
has been experienced in carrying the culture upon nutrient 
agar if it transferred as often as once in ten days. 
9. Temperature Relations. 
THERMAL DEATH-POINT.—The thermal death-point lies be¬ 
tween 49° and 50° C. 10 c.c. portions of nutrient broth, +15 
Fuller’s scale, in thin walled test tubes of resistance glass, hav¬ 
ing a uniform diameter of 16 to 17 m.m., were inoculated with 
two loopfuls of a 2 4 hour broth culture grown at 2 8° C. As 
soon as inoculated, the tubes were plunged into water of the 
desired temperature up to the cotton plugs, and kept there for 
exactly ten minutes. In order to insure a uniform temperature, 
the water in the water bath in which the exposures were made, 
was kept in constant motion by a horizontal paddle attached 
to a stirring machine and operated by a water motor. The dif¬ 
ferent temperatures were maintained by hand regulations with 
a Bunsen burner. At the end of the ten minutes exposure, the 
tubes were immediately cooled in cold water and subsequently 
allowed to develop at 2 8° C. Twelve tubes of broth were used 
for each temperature and determinations were made for each 
degree of temperature from 4 0° to 60° C. If turbidity ap¬ 
peared in any of the tubes within ten days, this was taken as 
an indication that the temperature to which the tubes were ex¬ 
posed was not fatal. 
OPTIMUM TEMPERATURE.—The optimum temperature lies 
between 2 8° and 30° C. 
ZTV 2 0 C., no growth occurs on nutrient agar, in nutrient broth 
or in the various sugar broths. 
