WILT OF CUCURBITS. 235 
November 20) diluted with four times its bulk of sterile water. The insects were allowed to feed 
until 1 p.m. Then the squash was removed and the beetles allowed to crawl over the bottom, top 
and sides of the’ moist infected glass dishes. At 4" 30" p.m. they were turned loose in the insect- 
cage. The next morning most of the beetles were at the top of the cage and had eaten but little. 
At 11" 30" I removed nearly all of the beetles and put them in dry, clean, glass dishes in order to 
starve them. They were left thus without food for 24 hours. I then sprayed the beetles and the top, 
bottom, and sides of the glass dish with the contents of a tube of potato-broth (culture of November 
20) mixed with a tube of sterile potato-broth to which an equal amount of sterile water was then added. 
The potato-broth-culture was faintly clouded with rolling clouds when shaken. It was examined 
in a hanging drop and one in perhaps 20 to 50 of the rods on the edge of the drop were found to be 
motile. At 1" 30" p.m. the dish was uncovered in the insect-cage and the beetles turned loose again 
after wetting down the pots and sand on the bench, inside and around the cage. Four days later 
(the twenty-sixth day from the beginning of the experiment) there was no trace of the wilt. Some 
of the Diabrotica vittata were feeding very slowly but most of them not at all. On the forty-first day 
4 out of 5 leaves on one of the vines were wilted, the lowest leaf and the upper leaves. These leaves 
had been all right in appearance the preceding day. Diabrotica vittata was still in the cage: 1 or 2 
had begun to eat a little of late but most of them were hibernating. 
On another plant in this cage the third and fourth leaves up yellowed and shriveled in December 
from serious gnawings but without suspicious signs. Sometime between January 1 and 4 the second 
leaf up wilted with signs regarded as suspicious. On the morning of January 4, the fifth leaf up showed 
a decided droop, although the earth was moist enough. ‘Twenty-four hours later 4 small leaves above 
the fifth leaf were wilted. The stem was green and turgid but there were no healthy leaves on the 
plant. The stem was now cut open and examined in several places, but no bacilli were found, and 
the cause of the wilt of the leaves remained uncertain. Possibly bacteria might have been discovered 
in the leaves. 
(38 a, 6, c.) Three pots containing 3 vines, 6 to 8 inches high, with 12 good leaves besides the 
cotyledons, were placed in an insect-cage at 1 p.m. with 15 or 20 specimens of the infected cucumber- 
beetle (Diabrotica vittata). The beetles began to feed at once and all but one or two were taken out 
at5p.m. Holes had been gnawed in the leaves of each vine. The next morning the vines appeared 
normal, only a trifle gnawed. The second day the vines looked very thrifty. The twentieth day 
more specimens of Diabrotica vittata were sprayed with a pure potato-broth-culture (tube 2, Novem- 
ber 20) and introduced into the cage. The next morning the beetles were at the top of the cage for 
the most part and had eaten but little. At 11" 30" a.m. I removed nearly all the beetles, starved 
them for 24 hours, sprayed them again (with potato-broth-culture of November 20—see 372, b,c) 
. and turned them loose in the cage as in the preceding experiment. The twenty-sixth day there was 
no trace of wilt. Most of the beetles were not feeding at all but some were eating slowly. The forty- 
first day there were still no signs. 
(39 a and 4.) A pot containing two vines, 16 and 17 inches high with 7 good leaves besides the 
cotyledons, were placed under a bell-jar after spraying both surfaces of each leaf. About 4 p.m. 6 or 
8 cucumber beetles (Diabrotica vittata) were turned loose on them. The next morning all the beetles 
but two were removed. The leaves were considerably gnawed. One of the remaining beetles was 
removed the afternoon of the second day and the other the third morning. The twentieth day there 
were no traces of wilt. (No further record.) 
(40.) One vine 4 inches high with 2 green cotyledons and 3 good leaves was placed under a bell- 
jar. About 20 specimens of Diabrotica viltata were introduced at 4 p.m. All went to the top of the 
bell-jar. The next morning all were removed. The leaves were riddled by bites. The seventh day 
the upper half of the upper leaf hung down flabby but without change of color. This leaf had been 
gnawed on both margins. Two days later (noon) 2 of the gnawed leaves showed very suspicious 
signs and the next morning the local wilt and change of color was unmistakable. Both leaves cer- 
tainly had the bacterial disease. This vine had been sprayed with a pure culture of Bacillus trachei- 
philus. The beetles were placed onit November 2, consequently the first unmistakable signs appeared 
ing days. On the tenth day at noon the leaves were more wilted. All the others were turgid although 
one was as badly bitten. At 4 p.m. a third leaf had changed color and wilted. This had been only 
slightly bitten. Evidently there were three distinct infections and perhaps more. On the eleventh 
day the three infected leaves hung down limp. On November 16 the vine had partly damped off 
at the surface of the earth. This was due to being watered too heavily the preceding day. (It was 
still under the bell-jar.) It had been going long enough to give striking results, however. The petioles 
were still turgid. On November 17, the vine was brought into the laboratory and examined micro- 
scopically. Bacteria were found in the vessels, and samples of the plant were saved in alcohol. 
Remarks.—Up to December 10 only four good cases appeared and all were upon 
sprayed plants standing under the bell-jars. Three were on plants punctured by the squash- 
