WILT OF CUCURBITS. 279 



3 sq. cm. This began in the pricked area and extended outward to the apex of the leaf. The leaf was 

 now cut off at the base of the petiole with a hot knife. None of the other leaves wilted as a result 

 of the inoculation. The basal leaves shriveled the fifteenth day, but from age, not from the wilt. 

 September 23 the plant was dry but bore a healthy green fruit. The diseased plants had been 

 bone-dry for weeks. 



(375-) This plant was 16.5 inches high and thrifty. The inoculation was made on the fifth leaf 

 8 inches from the stem. The pricked leaf-blade was 6.5 inches broad. Up to the fifth day at 

 10 a. m. no signs had appeared. Three hours later there was a slight wilt, and at 3 p. m. this involved 

 about I sq. cm. The wilt was on one side of the pricked area, and extended toward the margin of 

 the leaf. The next morning the wilted area did not exceed 2 sq. cm. Twenty-six hours later (July 23) 

 there were about 10 sq. cm. of wilt. I now cut off the leaf, with a hot knife, at its junction with the 

 stem. There were no constitutional signs until after July 27, but 8 days after the removal of the 

 leaf (July 31) the blade of the first leaf below and the first above drooped very decidedly. Between 

 this date and August 5 several of the leaf-blades farther up had wilted. On August 8 (the sixteenth 

 day after the removal of the pricked leaf) three more leaves above the inoculated one were wilted. 



(376.) This plant was 22 inches high. The fifth leaf was inoculated 10.25 inches from the stem. 

 The pricked leaf-blade was 5.5 inches broad. The seventh day after the inoculation (July 23, noon) 

 there were about 3 sq. crri. of wilt in and around the pricks. Two days later there was a wilted area of 

 about 15 sq. cm. extending a little over half-way to the base of the blade. I now cut away the leaf 

 close to the stem using a hot knife. There were no constitutional signs until after July 27. Six days 

 after the removal of the pricked leaf (July 31) the blade of the first leaf below and of the first two 

 leaves above drooped very decidedly. The eleventh day after the removal of the pricked leaf, I cut 

 away five leaves with wilted blades, all above the inoculated one. Three days later (August 8) two 

 more leaves above showed a decided droop of the blades. 



(377-) This plant was 14 inches high. The fifth leaf was pricked 7.75 inches from the stem. The 

 pricked leaf-blade was 5.5 inches broad. The first wilt was noted the seventh day in and around the 

 pricks. It then covered an area of about 2 sq. cm. Two days later (2 p. m.) about 7 sq. cm. of tissue 

 had wilted. The eleventh day (July 27) about 12 sq. cm. of tissue extending about one-third of the 

 distance to the base of the blade had wilted and changed color. The pricked area and the tissue 

 immediately around it were now dead. The leaf was cut off close to the stem with a hot knife. The 

 plant showed no constitutional signs until after August 5. Twelve days after the removal of the 

 pricked leaf the first leaf below was shriveled, probably from age, and the first leaf up showed a 

 decided droop of the blade due to the disease, I cut the petiole and saw the bacterial slime string out. 

 The next two leaves up showed a slight droop of the blades. Five days later (August 13) two more 

 leaves above the pricked one were wilting. 



(378.) This plant was 22 inches high. The fifth leaf was pricked 10 inches from the stem. The 

 pricked leaf-blade was 5.5 inches broad. The first wilt was noted at noon of the seventh day. It 

 then covered about i sq. cm. of the pricked portion. Two days later (July 25, 2 p. m.) the wilt 

 involved about 10 sq. cm. of leaf surface and reached nearly half-way to the base of the blade. I now 

 cut away the leaf at its junction with the stem, using a hot knife. There were no constitutional 

 signs until after July 27. Six days after the removal of this leaf (July 31) the blades of the first five 

 leaves up were drooping very decidedly. The leaves below had shriveled from age. Twenty days 

 after inoculation I cut away six petioles of wilted leaves to put into alcohol. The twenty- third day 

 August 8 one more leaf up showed wilt of the blade. The stem was still green and turgid. 



Remarks. — This experiment is in striking contrast to those of July 14 and 15. Everyone 

 of the twenty-four plants contracted the disease, and in each case it first appeared in the 

 pricked area. Nineteen of the plants subsequently developed constitutional signs and 

 died of the disease. No general signs appeared in the other five plants (Nos. 357, 368, 370, 

 372 and 374), i._ e., the disease was stopped by the removal of the affected leaf. In eighteen 

 cases the amputation of the affected leaf did not check the spread of the disease, but it is 

 apparent that a prompter removal of the pricked leaves, to wit, on the day the signs first 

 appeared, would have considerably increased the number of recoveries. This is deducible 

 from the fact that in those which did escape, the amputations were performed very promptly. 

 It is not likely, however, that this method of treatment will ever be recommended for 

 general use, since, in most cases, the wilt of the leaves would not be detected in time. 



The experiment was practically closed the forty- third day after inoculation (August 28) 

 but the plants stood on the bench in the hot-house until September 23. On that date all 

 of the diseased plants were bone-dry and had been so for several weeks. Three of the plants 



