WILT OF CUCURBITS. 219 
one additional vine has sickened naturally since my visit beginning August 22. This was all right 
until recently having only a few blighted leaves and withering petioles in the center of the hill, but 
now the whole of the big vine has wilted. 
There was no decided change in No. 10 until September 14, p. m. (after a rain which occurred 
September 13). Then a whole leaf was found wilted suddenly. This was not the nearest leaf to the 
one which I had infected and cut away, but the next nearest, 7. ¢., the ome on same side of the stem. 
This vine had been examined at 8.30 a. m. and found all right. At 6.30 p. m. this whole leaf had 
wilted. All the other leaves on the stem were upright. ‘Turgid sections were cut from the petiole 
of this wilted leaf and put into a moist place over night and next morning they bore the milk-white 
drops on the cut ends. Other portions were put into alcohol. [These petioles were examined in 
February, 1909, in thin sections under the microscope and bacteria were found in the vessels]. 
September 15, 10.30 a. m.: Five additional leaves were found wilted on this stem near the 
original source of infection, two toward the center of the hill and three beyond the original source 
of infection 1.5 feet. Now the nearest leaf had wilted, 7. ¢., the one on opposite side of stem. 
(11.) September 7: Many beads of the milk-white bacillus, which oozed from the cut end of 
squash-stems were stirred up in water and three large squash-leaves were pricked with a needle, 
not the one used for No. 9. ‘These were tied with torn rags to identify them; No. 9, by white 
cotton twine. On September 14, this plant showed 3 wilted leaves. 
PossIBLE CARRIERS OF INFECTION OF B. TRACHEIPHILUS. 
The following insects, identified for me by Mr. E. A. Schwartz, were found on diseased 
cucumber vines in 1893 and suspected by me at that time of being agents in the distribution 
of the wilt: Diabrctica vittata Fabr.; Diabrotica 12-punctata Oliv.; Strigoderma pygmeum 
Fabr.; Chauliognathus marginatus Fabr.; Epilachne borealis Kirby (lady beetle); Halticus 
uhleri Giard=H. minutus Uhler (Hemipter); Coptocycla guttulata (not especially devoted 
to the cucumber). 
INOCULATIONS OF SEPTEMBER 1, 1894.* 
One leaf on each of eight plants of Cucumis sativus, growing in the hothouse, was 
inoculated with bacteria taken directly from white beads oozing on the cut end of cucumber 
stems and squash-stems, the foliage of which was flabby or dying from the effects of the 
wilt-disease. A sterile steel needle was touched to the ooze from a cucumber-stem and 
twenty or thirty punctures were made in the center of the lamina of each of four healthy 
- leaves. The needle was then flamed and an equal number of pricks was made on the 
blades of as many more leaves using bacterial slime from the ooze on a diseased squash- 
stem. Plants 1 to 4 were inoculated from the cucumber; plants 5 to 8 from the squash. 
The bacterial ooze from the cut cucumber-stems was so gummy and viscid that it could be 
drawn out on the end of the needle in a delicate thread over a foot long. The bacterial 
masses did not dissolve readily in water, not even after several hours, nor with vigorous 
crushing and teasing. 
The temperature of the hot-house during the early part of the expermcut was high, 
as the following records show: Sept. 5, maximum 100° F.; Sept. 7, at 1" 50™ p. m., 99° F.; 
Sept. 8, at noon, 98°; Sept. 9, maximum 109°; Sept. 10, at 2" p. m. 104°; Sept. rr at gt 
a.m., 72°, noon 90°; Sept. 13, at 9" a.m., 72°, at noon go’. 
(1.) The first signs appeared the fourth day after inoculation and first in the pricked area. The 
sixth day the whole blade of this leaf was affected and drooping, and its apex beginning to dry out. 
All the other leaves remained healthy. The ninth day the blade of the leaf to each side of the pricked 
one was wilted. On September 11 the leaf-blade next above and the one below the pricked one were 
dry-shriveled, and the second leaf above showed change of color and wilt on one margin at the base 
of the blade. Twenty-seven hours later one-half of the blade drooped and had changed to that 
peculiar green characteristic of leaves wilted by the immediate presence of the bacteria. The other 
side of the leaf was expanded and turgid. ‘The disease progressed more slowly after the plant was 
brought into the cooler laboratory (September 10). On September 13 the whole of the pricked blade 
was wilted. On September 15 all of the leaves were wilted, 5 above and 1 below the inoculated 
leaf. The sixteenth day after inoculation the whole stem was dry-shriveled except the hypocotyl 
which was still turgid. 
*Those who wish to have etiologic proof without following all of the inoculations are advised to read only those 
of July 16, 1896, beginning on page 276. 
