WILT OF CUCURBITS. 227 



once on afruit. The record shows that in each case numerous delicate punctureswere made, 

 40 in one case and probably from 40 to 50 in the others. The infectious material consisted 

 of one part of the feebly clouded broth mixed with three parts of sterile water, viz., a part 

 of the same mixture that was sprayed on Nos. 20 to 23, just described. 



The day temperature during the first 10 days of this experiment generally ranged from 

 65 to 85 F. but once it was as high as 90 (November 4, noon) and once as low as 50 (early 

 morning of November 5). 



(24.) The middle basal part of the blade of the fifth leaf from the tip was pricked. The vine 

 showed no signs of the wilt until the morning of the eighth day. Then there was a wilted area about 

 1.5 cm. in diameter in the pricked portion. The rest of the leaf was turgid. By noon a v-shaped 

 area extending from the pricks to the end of the leaf had wilted and by night the whole tip and one 

 side had changed color and hung flaccid. The following day the entire blade of the pricked leaf had 

 collapsed although its petiole was turgid. No other leaves showed signs at that time. The tenth 

 day after inoculation the petiole of the pricked leaf was still turgid, as were also the leaves to either 

 side of the pricked one, and a pistillate blossom in the axil of the inoculated leaf. The morning of the 

 1 2th day the extreme tip of the petiole of the pricked leaf was slightly flabby. By late afternoon of 

 the same day the blade of the first leaf above the pricked one had wholly collapsed, except about 1.5 

 cm. around the apex of the petiole. There was no further change until the late afternoon 

 of the following day. Then the blade of the first leaf below the pricked one was flabby and 

 hanging down. The morning of the fourteenth day the blade of the pricked leaf was brown, the 

 petiole was still green but flabby at the extreme tip. The small fruit in the axil was green and looked 

 healthy. The second leaf down had lost its turgidity on one side. The second leaf above, which by 

 reason of longer internodes was three inches farther from the pricked leaf than the second below, 

 was still turgid. The vine bent in such a way that the second leaf down was 3 inches higher than the 

 pricked leaf or any above it. The stem was green and turgid. At 3 p.m. of the fifteenth day the 

 third leaf down was found to be flabby. No further records were made until 4 p.m. the nineteenth 

 day after inoculation. It was then found that the disease had proceeded gradually farther and farther 

 down the stem, wilting leaf after leaf until the seventh down had become flabby. In the morning 

 of the same day this leaf was turgid. The morning of the twenty-third day the vine was brought 

 into the laboratory and examined microscopically. The stem contained enormous numbers of 

 bacteria, which did not seem to be confined to the bundles but to be out in the parenchyma to some 

 extent as well. Part of the stem was shriveled but where the examination was made (4 to 6 inches 

 below the pricked leaf) it was still green and turgid. All the foliage had been shriveled for some days. 

 The upper part of the stem had also shriveled. The organism was cultivated out on November 17 

 into 4 tubes of potato-broth. On November 21, these four tubes were all alike, each being faintly 

 clouded with rolling clouds on shaking. Potato-cultures were made from these tubes. On November 

 26, three of these tubes contained pure cultures of B. tracheiphilus; the fourth was contaminated by a 

 yeast. The pure cultures on potato were thin, gray-white, wet-shining, and smooth, except that the 

 layer was not thick enough to hide the coarsest undulations on the surface of the potato. The cul- 

 tures were viscid to varying degrees (i mm. to 6 cm.). The most viscid one (No. 2) contained the 

 largest number of actively motile bacilli (one-half motile) . The color of the slime was almost exactly 

 that of the steamed potato itself. 



(25.) The middle basal part of the blade of the fifth leaf from the tip was pricked many times. 

 On the morning of the sixth day there were no signs. At i p.m. there was no change. At 2 p.m. 

 there was a very faint change of color in the pricked area. This was scarcely noticeable. At 2 130 p.m. 

 a piece of the leaf extending from the pricks to the apex had changed to a light green and wilted. 

 At 5 p.m. a sketch was made showing the wilted part shaded. This was now a decidedly lighter 

 green than the rest of the leaf (the change of color being much more noticeable than at 2 p.m.) and 

 there was a slight flabbiness at the tip. The leaf, with the exception of that part shaded in the draw- 

 ing, was turgid. The seventh day at noon the change in color (to light green) and the wilt were very 

 typical, extending from the middle pricked portion of the leaf to its apex. The apex of the leaf was 

 flabby and hung down. By 3 p.m. of the following day the whole blade of the pricked leaf had wilted. 

 The following noon (the ninth day after inoculation) the nearest leaf each way from the pricked one 

 had lost its turgor and was drooping a little. The petiole of the pricked leaf was turgid. At noon of 

 the tenth day after inoculation the leaves to either side of the pricked one had wholly collapsed and 

 the second leaf up was losing turgor. The second below was fully turgid. The petiole of the pricked 

 leaf was still green but slightly flabby at the tip. The blade was becoming brownish. The morning 

 of the eleventh day the second leaf above the pricked one was more flabby than on the preceding day 

 and the third above had lost its turgor. The second below was flabby and the fourth below was 



