WILT OF CUCURBITS. 261 



quantities of which were pricked into the three plants. The cucumber-fruit was still green 

 and firm but somewhat shrunken on the upper two-thirds and gummy drops had exuded 

 and dried down. The flesh, except in the center, where the seeds were, had, in most places, 

 a very decided water-soaked appearance but there was no soft-rot. The inoculations were 

 made as follows: The freshly cut surfaces of the gummy fruit were pressed down gently 

 on the leaf from opposite sides several times and then in each case about twenty needle- 

 pricks were made through this moist surface. 



(221.) Muskmelon (Cucumis melo). This was a small vine bearing six leaves. The pricked one 

 was the third leaf up and its blade was about 2 inches broad. It was inoculated in two places, i. e., 

 there were two groups of pricks. The ninth day there were wilted areas centering in the pricked spots 

 and covering in each case an area of about i sq. cm. The change of color (to a dull faded green) was 

 decided. Four days later the petiole of the pricked leaf was still turgid. The blade of the first leaf 

 up was slightly flabby. The next below was turgid but the blade of the second below had collapsed. 

 This second below was the first leaf above the cotyledons and came out on the same side of the stem as 

 the pricked leaf. Seventeen days after inoculation (December 3) the vine was badly wilted. The 

 blades of all of the leaves had collapsed and the stem was beginning to shrivel near the base of the 

 pricked leaf. It was now brought into the laboratory for minute examination. The stem was first 

 cut near its juncture with the pricked leaf. The vessels here were full of bacilli some of which had 

 flooded out into the parenchyma, but the cross-section was not sticky. The rods were not motile. 

 An inch or two lower down the cut surface of the stem was sticky. An inch or two above the first cut, 

 the vessels were crowded full. Some of the bacteria were motile. There also the cut surface was 

 sticky. Cultures were made December 3 into tubes 5, 6, 7 and 8 of November 20 (which had failed). 



(222.) Cucumber (Cucumis sativus}. This vine was inoculated in the 

 same way as the preceding. The pricked leaf was the third from the cotyle- 

 dons and its blade was 4.25 inches broad. It received four sets of pricks, 

 two on each side of the blade near its margin and about an inch apart. The 

 ninth day on one side there was a wilt spot, about 2 sq. cm. in size, centering 

 in one of the groups of pricks. On the other side there was a wilted area 

 covering about 5X2 cm., including both sets of pricks. The change of color 

 was decided. It is probable that signs appeared on this and the preceding 

 vine the previous afternoon. This would make the time of incubation 8 

 days. Two days later about half of the pricked blade had wilted. The 

 thirteenth day nearly the whole of the pricked blade had shriveled and 

 changed color. The petiole was turgid and all the rest of the plant was 

 normal in appearance. The seventeenth day the vine was 15 inches long. 

 The first four leaves above the pricked one were now flabby. The petiole 

 of the pricked leaf and of the first two above it were still rigid. Those of the next two, which were 

 younger and softer, were flabby. The uppermost wilted leaf was 8 inches above the node of the 

 pricked leaf. The first leaf below (2 inches down) was turgid at 9 a. m. but at noon was slightly 

 flabby on one side. On December 7, bacterial slime from this plant was used for further inocula- 

 tions (see 226, etc.). Bacteria taken from the vessels were not clearly motile. 



(223.) Winter Squash (Cucurbita sp.). One leaf was inoculated. Five sets of pricks were made, 

 the method of inoculation being the same as that in the two preceding cases. The ninth day there were 

 no signs. The eleventh day the tip of the pricked leaf had wilted over a space of about a square 

 centimeter. The thirteenth day the tip of the pricked blade had recovered its turgor but was yellowish. 

 The seventeenth day the vine was about two feet long and vigorous. It looked much as if the bacteria 

 would not get out of the pricked leaf into the stem. The leaf still preserved its color and turgor except 

 a few square centimeters at the tip of the blade which was yellowish and alternately turgid and flabby 

 (see fig. 73). The dots indicate the pricked parts and the shaded apical portion the only part which 

 was wilted at the time. December 13 (27 days after inoculation) the pricked areas were dead and the 

 leaf was yellow around them. There was no wilt and most of the blade was green. December 31 

 three basal leaves including the pricked one, which had become gradually yellow, were shriveled but 

 though I had watched this plant carefully for many weeks the disease gave no indication of spread- 

 ing from the pricked leaf to other parts of the plant. 



Remarks. The bacillus used for these inoculations was taken, it will be remembered, 

 from the interior of a green cucumber-fruit. In spite of its appearance I was in some doubt 



*FiG. 73. Leaf of squash No. 223, inoculated with Bacillus tracheiphilus (cucumber strain) Nov. 16, 1895. Plant 

 very resistant. The shaded area was wilted on Dec. 3. Less than natural size. 



