268 BACTERIA IN RELATION TO PLANT DISEASES. 



Inoculations of February 26, 1896. 



A set of inoculations was made in the hothouse at 2 p.m., from a white, wet-shining, 

 sticky culture of Bacillus tracheiphilus on steamed carrot (tube 2 February 18, from 1, 

 February 13 which was a potato culture made from a fermentation-tube (No. 1, January 20) 

 containing cane-sugar. The plants inoculated were: Benincasa ccrifera, Cucurbita focti- 

 dissima, Cucurbita califoruica, cucumber, muskmelon, watermelon and Datura stramonium. 

 Numerous bacteria were put in with each inoculation, which was made with a sharp- 

 pointed steel needle. All of the plants were examined on February 28 and February 29, 

 and were free from disease. 



(272.) Benincasa ccrifera. This was a small plant having three leaves besides the green coty- 

 ledons. Many pricks were made on the middle leaf . The plant appeared healthy on March 5. The 

 first signs were noted on March 6 at 2 p. m. (end of the eighth day) at which time there was a slight 

 wilt extending outward from the pricks to the margin. The following day fully half of the pricked 

 leaf had wilted. Two days later the whole of the blade of the pricked leaf had wilted, as also that 

 of the first leaf above and below. The sixteenth day the leaves were badly shriveled, but the stem 

 was normal. Material was saved in alcohol. On microscopic examination enormous numbers of 

 bacteria were found in the vessels (slide No. 202). 



(273.) Cucurbita foetidissima. This vine was grown from seed planted October 11, and at 

 the time of inoculation had eight good leaves. Many pricks were made on the under side of an 

 upper leaf. The fifth day (9 a. m.) the leaf looked suspicious and at i h 2o m p. m. there was distinct 

 wilt at the tip and a dull green color where pricked. The following day there was little change. The 

 next day the pricked area had changed to a whitish green and the terminal one-fifth of the blade 

 hung flaccid. The following day about one-third of the leaf was wilted and 2S hours later (close of 

 eighth day) there was a bad collapse of two-thirds of the pricked blade. The beginning of the eleventh 

 day the whole of the blade of the pricked leaf had wilted but the petiole was still rigid. The blades 

 of the first and second leaf up were now inclined to droop. Two days later the blade of the first leaf 

 down was wilted. All the petioles were still rigid. The sixteenth day all the leaf blades had shriveled. 

 The stem and petioles (lower two-thirds) were normal. The plant was put into alcohol. On micro- 

 scopic examination the bundles of the petiole of the inoculated leaf (fig. 77) were found filled with 

 bacteria and badly disorganized (slide No. 254). The bacteria also extended into the bundles of the 

 fleshy root but here the disorganization was less. 



(274.) Cucumber (Cucumis sativus). This was a thrifty young plant. Many pricks were made 

 on the tip of an upper leaf. The fifth day (9 a. m.) there was wilt and change of color in an area of 

 10X3 mm., along one side of the pricked area which was about 10X 10 mm. in diameter. At 1 h 20 

 p.m. of the same day the wilted area was twelve times as large. The following morning there was 

 little change, but 24 hours later the terminal eighth of the leaf was drooping. The next day the 

 change of color in the wilted area was more decided but the latter had not increased much. At the 

 end of the ninth day there was very striking wilt confined to the terminal half of the pricked leaf, 

 a wedge-shaped area 7.5 em. long by 2.5 cm. wide (in the widest portion). It was dull green and the 

 tip was drooping. Twenty-five hours later the whole of the blade of the pricked leaf had wilted. 

 The rest of the vine was normal. On March 9, the blades of the first two leaves above and the first 

 two below had wilted but the petiole of the pricked leaf was still rigid. Five days later (seventeenth 

 day) the vine was badly wilted and was pulled up for microscopic examination. The stem was green 

 and turgid but its vessels contained a stick}' bacterial slime which strung out in long, delicate threads. 

 The middle part of the stem was saved in alcohol. 



(275.) Cucumber. This was an old plant. Many pricks were made on the blade of an old, 

 upper, whitish leaf. On March 3, at 10 a. m., there were no signs but 24 hours later half of the leaf 

 was flabby and drooping, on the pricked side. It was now nearly 7 days since the leaf was pricked. 

 The following day the whole of the pricked blade was dry shriveled and the tip of the petiole was 

 slightly flabby. On March 6 (end of ninth day) the petiole had shriveled. The rest of the vine was 

 normal. The following day there were constitutional signs. By 10 a.m. of March 9 everything 

 had collapsed except the green stem and a few small basal leaves. 



(276.) Cucumis melo var. dudaim. This was a small plant. Many pricks were made on one 

 li ii blade. The fifth day there was slight wilt in the pricked portion and running out to one margin 

 of the blade. The following day there was little change, but 24 hours later the whole pricked leaf 

 was droi iping. This, however, was favored by a dry soil because, on watering, the leaf recovered its 

 turgor in the afternoon with the exception of the tissue immediately around the pricks. The next 

 morning the pricked leaf was turgid with the exception of a wedge-shaped piece extending from the 



