144 
Journal of Agricultural Research 
Vol. XXV, No. 3 
tion of leaves and pedicels. When free from disease, the plants con¬ 
tinue to grow and set pods until frost, which in the vicinity of Madison, 
Wis., is usually not earlier than September 10. Such an outbreak in 
commercial fields would cause a considerable reduction in yield. Aside 
from this epidemic, however, the disease has been of little practical 
importance except late in the season of 1921, when it caused heavy 
infection of the leaves. 
Except for the probability of the organism being carried over on the 
infected seed, nothing is known of the method of overwintering. In 
Wisconsin, even though the young seedlings become infected, it appears 
that subsequent weather conditions are, as a rule, unfavorable for further 
development of the disease. With such sporadic outbreaks the disease 
will probably never be of any great economic importance under Wis¬ 
consin conditions. In States where the lima bean is grown commer¬ 
cially the disease should be considered a factor of economic importance, 
provided that the climatic conditions are favorable for its development. 
THE ORGANISM 
ISOLATION 
# Microscopic observations of sections of young lesions show the invaded 
tissue to be swarming with bacteria. The organism was isolated from 
the leaf tissue in practically pure culture by dipping the diseased tissue 
in 95 per cent alcohol for an instant, immersing in mercuric bichlorid 
(1 to 1,000) for one minute, rinsing through three or four sterile water 
blanks, and crushing in a tube of beef broth. After one-half to one hour 
dilution plates were poured from the tube of macerated tissue. 
In the isolations from stems and pods a wet-shining, rapidly-growing, 
yellowish organism almost invariably appeared on the plates along with 
the white organism, but several inoculation experiments proved that it 
was not pathogenic. Pure cultures of the pathogenic organism have been 
obtained by touching a drop of the exudate on pods .with a sterile needle 
and transferring directly to agar slopes. 
During the course of investigations a number of strains of the organism 
have been isolated each year and successful inoculations made with them. 
A comparison of cultural characters showed that all were quite similar. 
The first strain isolated, designated ia, has been studied most intensively 
and is presented as the type strain. 
MORPHOLOGY 
# The organism is a short rod with rounded ends, usually occurring 
singly or in pairs in young cultures. Short chains have been observed 
in old agar cultures and in beef-peptone broth containing 4 per cent 
sodium chlorid. When stained from 3-day-old beef-peptone agar cultures 
with gentian violet or Loeffler’s methylene blue, the cells measure from 0.3 
to 0,7 n in diameter and from 0.7 to 2.2 n in length, averaging 0.5 by 1.5 /i. 
Both Caesar-GilTs and DuckwalTs modification of the Pitfield flagellum 
stains have shown the organism to be motile by one to several polar 
flagella (PI. 3, C). No endospores or involution forms have been observed. 
Capsules were not demonstrated by Welch's staining method from 
potato agar, nutrient agar, or nutrient broth cultures. The organism is 
gram negative and nonacid fast. 
