BACTERIAL WILT OF CUCURBITS. • 25 
arose, which at first somewhat resembled Bacillus tracheiphilus. Later, on beef -agar 
slants, this type gave a dense, opaque, somewhat yellowish and rapidly growing 
colony. A second type {B) was constantly found in the plates poured from one set of 
dilutions. This isolation (B) more closely resembled the wilt organism, and young 
colonies on beef agar were at first scarcely to be distinguished. Even the rate of 
growth was about the same as for Bacillus tracheiphilus. However, old colonies are 
Bomewhat more opaque and also have a very slight yellowish cast not present in the 
wilt organism. The organism also produces more alkali than B. tracheiphilus. Inocu- 
lation tests on cucumber plants have given negative results with both these types of 
bacteria. Occasional colonies of other bacterial and fungus types came up on the 
plates, but on account of their rarity were considered as contaminations. The wild 
organism was not obtained. 
Portions of intestines left from each beetle dissected were retained and in each 
case were used in inoculating a single young cucumber plant by needle puncture. 
One plant only out of the ten wilted, but isolation was not attempted. There were 
at the time a large number of other cucumber plants in the greenhouse, all of which 
were free from wilt, and there is little doubt that the plant in question had become in- 
fected with the true bacterial wilt. 
It was thought worth while to test the types of intestinal bacteria in mixet 
culture with authentic isolations of Bacillus tracheiphilus for possible antagonism. 
After three weeks in mixed cultures (beef agar plus 1 per cent cane sugar) young 
cucumber plants were inoculated by needle punctures in the leaves; and other plants 
were inoculated as checks with intestinal types A and B alone and with the wilt organ- 
ism alone. Of ten plants inoculated with cultures of A plus wilt, and of the two plants 
with A and B alone, none became infected; but of four plants inoculated with B plus 
wilt all contracted wilt, showing the typical stringy ooze from the cut stems and the 
vessels filled with bacteria. All plants inoculated with B. tracheiphilus alone showed 
wilt. The plants were under observation one month. 
In another experiment using four plants with type B alone, four plants with the 
wilt organism alone, eight plants with A plus wilt, and four plants with B plus wilt, 
all from 2-weeks-old cultures, the results were identical — growth of B. tracheiphilus 
and infection in the presence of B; none in the presence of A. 
The wilt organism itself was not isolated on agar-poured plates 
made from, beetle intestines, but evidence was adduced that the 
organism was present in the intestines of one of the ten beetles used 
and that in the presence of cane sugar the intestinal flora of at least 
one beetle was not antagonistic to the wilt organism, but that in the 
majority of the cases the intestinal flora (type A) was under these 
conditions antagonistic to the wilt organism. 
These results, while not sufficient to warrant far-reaching con- 
clusions, suggest the possibility that a careful study of the bacterial 
flora of cucumber-beetle intestines will afford an explanation of the 
fact that only a small proportion of wilt-fed beetles are wilt carriers. 
VIRULENCE TESTS. 
During the interval since August, 1914, several hundred isolations 
of Bacillus tracheipfiilus have been made from cucumber, cantaloupe, 
winter squash, crookneck summer squash, and cymling, and from an 
area extending from Canada to southern Georgia and Long Island to 
Iowa. Of these isolations from various hosts and localities, over one 
