228 



BACTERIA IN RELATION TO PLANT DISEASES. 



turgid. (The third down was wanting except the base of the petiole.) The next morning all the tiny 

 leaves at the tip (beyond the second leaf up) had collapsed. By 5 p.m. of the same day the wilted 

 leaves had begun to shrivel. The fourth down was still turgid. The fourteenth day the fourth leaf 

 had lost most of its turgor. The petiole of the pricked leaf was still green but it was flabby nearly 

 to the base. The blades of the first and second leaves below had shriveled, also those of all the leaves 

 above the pricked one. The upper part of the vine was now removed for examination and cultures. 

 The vessels were found to be full of the bacillus which strung out in fine gummy threads from the 

 cut surface of the stem when a needle-tip was touched to it and withdrawn. The bacteria were 

 exceedingly abundant and the inner tissues were considerably broken down. The organism was cul- 

 tivated from this portion of the vine at different heights, inoculations being made from the stem into 

 potato-broth from which a pure culture of Bacillus tracheiphilus was subsequently obtained on 

 steamed potatoes. 



The fifteenth day the fifth leaf down was flabby. The twenty-ninth day this plant was removed 

 together with the other old cucumber vines, to make room for squashes. Dry material was saved 

 from this vine for the herbarium. A futile search was made in it for spores of the bacillus. 



(26.) The fifth leaf from the tip was pricked many times in one of the side lobes. At 10 a.m., 

 October 3 1 there were no signs but by i h 30'" p.m. of the same day the pricked lobe had wilted. The 

 first signs appeared, therefore, in this case at the end of the sixth day, the inoculations having been 

 made in the afternoon. By noon of the seventh day the wilt and change of color had made marked 

 progress in the pricked lobe and that portion of the latter in which the wilt first appeared had dried 

 out. The temperature in the hothouse when this observation was made was 80 F. The following 

 day (3 to 4 p.m.) the whole leaf-blade was flabby. The pricked portion was dry-wrinkled, the petiole 



Fig. 60.* 



turgid. There was no further change until noon of the tenth day. Then the petiole of the pricked 

 leaf was slightly flabby at the apex but still green. The blade was turning brownish on the pricked 

 side. The nearest leaf to each side was turgid. At 4 p.m. the following day, the first leaf below had 

 fully collapsed although turgid at 10 a.m. The second leaf above was still turgid. (The first leaf 

 above was wanting, only the base of the petiole remaining.) The upper part of the vine hung down 

 in such a way that the lower (collapsed) leaf was uppermost. The morning of the twelfth day the 

 petiole of the first leaf below the pricked one was flabby. An observation made at 5 p.m. showed no 

 further change. The morning of the fourteenth day after inoculation the blade of the pricked leaf 

 was brown and dry-shriveled throughout. The petiole was still green and it was flabby only at the 

 tip. The second, third, and fourth leaf down were flabby as was also the petiole of the second 

 leaf. The blades of the fifth and sixth leaves below (all that remained) were flabby and shriveled 

 including the petioles. This latter seemed anomalous. The petiole of the first leaf below was flabby 

 and shriveled to its base although still green. It was in a much worse condition than the pricked leaf. 

 Here we probably have to take into account the smallness of the pot and the age of the vine, the 

 lower leaves being weaker than the others. The twenty-ninth day the plant was pulled up to make 

 room for squash vines. A portion of it was saved dry for the herbarium. Unavailing search was 

 made in it for spores of the bacillus. 



(27.) The seventh leaf from the tip was pricked many times in the center of the lamina. There 

 were no signs until the morning of October3i (5! days). Then the pricked leaf was wilted in a V-shaped 

 area opening outward from the pricks to the apex of the leaf. In the afternoon the condition was 

 that shown in fig. 60. The apex was drooping. The rest of the leaf was normal. The following noon, 



*FiG. 60. Bacterial wilt at 4 p. m., Oct. 31, on an inoculated leaf of cucumber plant No. 27. For condition 20 

 hours later, see fig. 6r. Leaf pricked Oct. 25, 1904. First signs of wilt (darker shaded part) morning of Oct. 31. 

 Drawn by Theodore Holm. 



