274 BACTERIA IN RELATION TO PLANT DISEASES. 



the petiole, and the wilt had extended to five leaves above (16 inches of stem) and to 3 leaves 

 below. The stem was still green and looked normal; also the leaves farther up and lower down. 

 On July 14 the whole plant, which was several feet long, had been shriveled for some days. 



(312.) Cucumis erinaceus. On the ninth day there was a slight yellowing of the pricked part 

 and of the apex of the blade beyond the pricks, but no wilt. Two days later there was very little 

 change. July 14 the pricked leaf had dry-shriveled to the stem but the rest of the plant was normal 

 and was making a good growth. August 15 the plant was living and growing, having overcome the 



disease. 



(313.) Cucumis erinaceus. The ninth day this plant resembled the preceding. July 14 a few 

 leaves had dry-shriveled but the bulk of the plant was uninjured and the wilt seemed to have 

 stopped. August 15 the plant was still living and growing. It had overcome the disease. 



(314.) Cucumis erinaceus. The seventh day only about two-thirds of the small pricked leaf 

 had wilted and 2 days later the signs were still slight. Part of the pricked leaf-blade had dried out 

 and the lower edges were curved in and flabby. The leaf above resembled this one in being incurved 

 and slightly wanting in turgor. The eleventh day the wilt was still confined to the pricked leaf and 

 the first one above, the internode between the two being very short. On July 14 the pricked leaf 

 was dead and the tip of the branch bearing it; also some leaves lower down. Midway, however, 

 were three good leaves. The other branch (the plant was a small one) looked healthy and it seemed 

 at this date as if the plant would outgrow the disease. On August 15 this plant, like the two preced- 

 ing, was living and growing, having overcome the disease. 



Remarks. The result with the watermelon confirmed the previous experiments. 

 This plant is very resistant. 



Cucumis erinaceus, Apodanthera undulata, Cucurbita palmata (?), Cucurbita digitata, 

 and Trichosanthes cucumeroideswere quite resistant. Some developed no signs; others only 

 local ones; three developed constitutional signs, but recovered after a few weeks. Passi- 

 flora incarnata is resistant. 



Cucurbita foetidissima. Cucumis melo var. dudaim, and Echinocystis lobata contracted 

 the disease promptly and were destroyed by it. 



INOCULATIONS OF JULY 14, 1896. 



This set of experiments was made to determine whether the disease could be cut out. 

 Twenty muskmelon plants (Cucumis melo) were inoculated in the hothouse from tube 

 No. 12, July 8 (a potato culture made from a peptonized beef-bouillon culture which had 

 been subjected to intense cold in a mixture of frozen carbon dioxide and ether) . On July 

 1 1 , the surface of the potato in this tube bore a good typical growth of Bacillus tracheiphilus . 

 It was smooth, wet-shining, white, i. e., almost exactly the color of the steamed potato, 

 and quite sticky. All inoculations were made on the leaf -blades and as far as possible from 

 the stem. From 30 to 60 delicate pricks were made with a steel needle sterilized in a flame 

 and cooled each time before using. The pricked area in each case was less than i sq. cm. 

 A loop of fluid from the bottom of the culture was taken out on a sterile platinum loop, 

 placed on the clean surface of a leaf and the pricks were then made in and around this 

 wetted surface, the drop being finally spread so as to cover all the pricks. A clean paper 

 was then placed over the pricked leaf to screen off the bright sun. 



(315 to 334.) Twenty muskmelons. Next to the lowest leaf of each plant was inoculated on the 

 blade 3 to 5 inches from the stem. 



July 3ist. There has been no trace of wilt on any of these 20 plants. 



Remarks. All the melons were of one variety, the New Early Hackensack. My plan 

 was to cut away each pricked leaf at its junction with the stem as soon as a trace of wilt 

 appeared, but the entire experiment miscarried. Up to July 31, none of the 20 plants had 

 contracted the disease. Several hypotheses occurred to me as explanations of this failure: 

 (i) The plants were of a resistant variety; (2) The wrong organism was used; (3) The cul- 

 ture was dead when taken into the hothouse or, at least, that part of it in the fluid at the 

 bottom of the tube; (4) The bacteria were destroyed by the bright sunlight in the short 

 time which elapsed between spreading them on the leaf and pricking them in; (5) The 

 intense heat of the hothouse detroyed them. The day was very hot and the sun bright. 



