WILT OF CUCURBITS. 257 



Inoculations of October 5, 1895. 



A new set of inoculations was made in the hothouse, at 3 p. m., on young cucumbers 

 (Cucumis sativus) , gherkins (Cucumis anguria) , young muskmelons (Cucumis melo) , and young 

 squashes (Cucurbita sp.), using sticky bacterial ooze from the interior of a cucumber-stem 

 obtained from a field of late cucumbers a few miles northwest of Washington. The bac- 

 teria were very sticky and strung out a long distance from the cut end of the stem. The 

 stem was examined microscopically and found to contain many vessels gorged with a 

 bacillus. I washed the surface of the stem, then shortened it several times with a razor, 

 and finally with a flamed needle pricked the oozing bacteria into the healthy plants. The 

 wet sticky surface of the stem was also pressed down on the surface of the leaves and many 

 delicate needle-pricks were made within the wetted area. Especial pains was taken in each 

 case to make the infection thorough. The plants were 6 to 8 inches high except the gherkins 

 which were smaller. All the inoculations were made on the leaf-blades. 



(205.) Cucumber. The ninth day the pricked leaf had changed color and was drooping but the 

 petiole was rigid. The blade of the next leaf up also drooped some but was a healthy green. Twenty- 

 four hours later the blades of two more leaves were wilted but the petioles were still rigid. The 

 cotyledons were not yet wilted although on nearly the same level as the base of the petiole of the 

 pricked leaf. The eleventh day the cotyledons were drooping but all the petioles were rigid as also 24 

 hours later. The fourteenth day the vine was brought into the laboratory and examined. All the 

 foliage had wilted and the stem near the earth had bowed over. Otherwise it was normal in external 

 appearance. The upper part of the stem was cut and examined microscopically. The juice was 

 sticky and stringy and the vessels were full of a bacillus which had also flooded out into the surround- 

 ing parenchyma and was motile. The rods were all nearly the same size. The stem was cut cross-wise 

 with a hot knife and dug into with a hot needle and from the cavity thus made bacteria were removed 

 for eight cultures: No. 1, old alkaline potato broth; No. 2, streak on alkaline agar; Nos. 3 to 8 

 potato cylinders. The agar failed ; all the potato-tubes developed typical cultures of B. tracheiphilus 

 of which four were exceedingly sticky, one moderately sticky, and one only slightly sticky (obser- 

 vations after 5 days). 



(206.) Cucumber. The ninth day half of the pricked leaf-blade was drooping. The rest of the 

 plant was normal but 24 hours later the blade of the first leaf up had wilted. The cotyledons which 

 arose from nearly the same level as the pricked leaf showed no sign of the w r ilt. The petioles were 

 still rigid. The following day the blade of the next leaf up had wilted. The cotyledons and all the 

 petioles were rigid. Twenty-four hours later one of the cotyledons was drooping. The blades of 

 the wilted leaves were badly collapsed but the petioles were still turgid. Four days later (the six- 

 teenth day after inoculation) all the leaf-blades had shriveled and also the apex of the petioles. The 

 twenty-third day the whole plant had shriveled. 



(207.) Cucumber. By the end of the ninth day the entire blade of the pricked leaf had changed 

 color and wilted. The blade of the first leaf up was also drooping but was of a good green color. 

 Twenty-four hours later one of the cotyledons hung limp. The petioles were rigid. The following 

 day the second leaf up began to roll at the edges. The twelfth day after inoculation the second 

 cotyledon was drooping. The petioles of the wilted leaves were still rigid but the blades were badly 

 collapsed. Four days later the blades and tip of the petiole were shriveled. The twenty-third day 

 the whole plant was shriveled. 



(20S. ) Muskmelon. The ninth day after inoculation the pricked blade changed color and showed 

 a trace of wilt centering in a group of pricks. The total affected area was only a few square milli- 

 meters. The following day there was very little increase of the wilt, scarcely 2 sq. mm. Twenty-four 

 hours later about one-third of the blade of the pricked leaf was plainly wilted. The following day 

 more than two-thirds of the pricked blade had changed color and was drooping. The petiole was 

 rigid. Four days later the blade of the pricked leaf had shriveled but the petiole was turgid. The 

 next two leaves above now had wilted blades. A week later the whole plant had shriveled. 



(209.) Muskmelon. The ninth day the tissue in one small group of pricks was dead. Three 

 days later there was a small amount of wilt near the margin. The twenty-third day the pricked 

 parts were dead and the tissue around them was yellow. The tip of the leaf had wilted slightly. The 

 twenty-sixth day the entire pricked leaf-blade had wilted and that of the next leaf up. 



(210.) Muskmelon. By the end of the ninth day the entire blade of the pricked leaf had wilted 

 and changed color. The petiole of the pricked leaf was rigid. In 24 hours the wilt had increased 

 somewhat but the petiole was still rigid. The following day the pricked leaf-blade and one coty- 



