Apr. 15, 1921 
Bacterial Spot of Tomato 
131 
Isolations were made from material collected at Indianapolis, Frank¬ 
fort, and La Fayette. From all of these sources and all types of lesions 
the same type of yellow, translucent, rapidly growing bacterial colony 
was obtained. Numerous strains were isolated by transfer to agar 
slants, and all exhibited similar cultural characteristics. The patho¬ 
genicity of a number of these strains was proved by numerous successful 
inoculations in the greenhouse with subsequent reisolation and in many 
cases reinoculation. These tests are discussed on a succeeding page. 
Strains used to any extent were tested for freedom from contamination 
by poured plates. For the detailed morphological and physiological 
study, two strains were used, one isolated from a fruit collected at La- 
Fayette, the other from a leaf collected at Indianapolis. These were 
proved pathogenic by repeated inoculation and reisolation, and their 
purity was proved by poured plates. No marked differences were noted. 
The strain isolated from pepper fruit has not yet been carefully studied. 
MORPHOLOGY 
The organism is a medium-sized rod with rounded ends, usually occur¬ 
ring singly or paired, occasionally in short chains. The cells stain readily 
with Ziehl's carbol fuchsin, anilin gentian violet, and Loeffler’s methy¬ 
lene blue. Frequently two heavily staining portions are visible, one at 
each end of the rod. Age of the culture does not appear to affect the 
size measurements. When stained with Loeffler’s or Van Ermengem’s 
flagella stains, the cells vary in width from 0.65 to 1.35 n and in length 
from 1.44 to 2.79 fi t with an average of 0.85 by 1.94 /x, as measured with a 
vernier micrometer. 
The organism is motile by means of one polar flagellum (PI. 28, B). 
The flagella were stained by Morrey’s modification of Loeffler's method 
and more readily by Van Ermengem’s method, in which, by necessity, 
pyrogallic acid was substituted for gallic acid in the formula. Flagella 
were found in both old and young cultures. The best stains were 
obtained from 24-hour beef agar slant cultures. 
Endospores and involution forms have not been noted. It has not 
been possible to demonstrate the presence of capsules by the Welch or 
Hiss methods in stains made from beef, potato, or blood agar. However, 
in greatly enlarged photomicrographs made from Van Ermengem flagella 
stains, a narrow but distinct clear zone or halo about each rod indicates 
the presence of a thin capsule. The organism is Gram-negative. 
cultural characters 
The organism grows very readily on a wide variety of culture media. 
For general laboratory use a 2 per cent potato agar with 2 per cent 
peptone was found most satisfactory. In the following studies cultures 
were incubated at 25 0 C. unless otherwise specified. The reaction of 
