264 BACTERIA IN RELATION TO PLANT DISEASES. 



Inoculations of December 7, 1895. 



Inoculations were made at 2 p. m., into gherkin {Cucumis anguria), cow-pea (Vigna), 

 muskmelon {Cucumis melo), and cucumber {Cucumis sativus), using sticky bacterial slime 

 out of the vessels of cucumber-vine No. 222. Great quantities of the bacteria were used. 

 A limited area of the surface was first thoroughly wetted with the sticky slime and then 

 many needle-pricks were made into this portion. 



(239.) Gherkin. Four days after inoculation (between 10 a. m. and i p. m.) the tip of the pricked 

 leaf changed color and commenced to wilt. The ninth day the plant, which was a small one, had 

 collapsed. 



(240.) Cow-pea. The twenty-fourth day there was no wilt or death of the tissue. Up to March 

 4, there had been no result from the inoculation. 



(241.) Muskmelon. The third day there was a small wilted spot including each of the five sets 

 of pricks. An enormous number of bacteria were pricked in and this was supposed to account for the 

 unusually short time between inoculation and the first signs, i. e., only 68 hours. There was little 

 increase of the wilt, however, during the next 24 hours. On the sixth day signs were uncertain. The 

 twenty-fourth day the leaves were spotted and the vines were not thrifty but it was doubtful if the 

 bacteria were stiU alive. Up to March 4 there had been no other result from the inoculation. 



(242.) Cucumber. This was a large plant. The fourth day the vine showed no signs of the wilt. 

 Two days later the case was doubtful but the ninth day the blade of the pricked leaf was dry-shrivel- 

 ing. The twelfth day the leaves above and below were turgid. Twenty-four days after inoculation 

 (December 31), the stem was collapsing, all the leaves having shriveled some days ago. The stem was 

 now cut open and the interior found to be full of a white sticky mass of bacteria. Inoculations into 

 244 and other vines were made direct from the interior of this plant. A loop of slime taken from the 

 interior of 242, with bacteriological precautions, and spread on slant agar, yielded a pure culture 

 which was used to inoculate No. 251, etc. 



(243.) Cucumber. This was a big plant. The fourth day (i p. m.) the inoculated leaf had changed 

 to a pale green and had begun to wilt around one of the five groups of pricks. The period of incubation 

 was nearly four days. Two days later one-fifth of the pricked blade hung flabby and had become a 

 dull green. The ninth day the blade of the pricked leaf was shriveling. The twelfth day three leaves 

 above the pricked one were wilted. They had been turgid the day before. The first leaf below was 

 normal. The twenty-fourth day the stem was collapsing. All the leaves had shriveled some days ago. 



Remarks. — The cow-pea did not contract the disease. The three closely related species 

 of curcurbits contracted the disease. 



Inoculations of December 31, 1895. 



Three cucumbers {Cucumis sativus) and four squashes {Cucurbita maxima) were 

 inoculated in the hothouse, at 9 a. m., with a white sticky mass of bacilli from the interior 

 of cucumber- vine 242 (cucumber-strain) . The bacterial slime was pressed out on the leaves 

 and then pricked in with a sterile steel needle. Many pricks were made. In some cases 

 the bacteria were put on the dorsal side, in others on the ventral side of the leaf. Bach of 

 the cucumbers was inoculated on one leaf, each of the squashes was inoculated on one 

 green cotyledon. 



(244.) Cucumber. The eighth day (10 a. m.) there was wilt on one margin of the inoculated leaf 

 extending outward from three groups of pricks — 5X i cm. The blade of this leaf was 4 inches broad. 

 There had been no wilt the preceding afternoon. The tenth day the whole of the pricked blade was 

 wilted. Other leaves were normal. The sixteenth day the petiole of the pricked leaf was still turgid 

 to the tip but the blade had dry-shriveled. All the leaves above the pricked one, four in number, were 

 wilted. The blade of the first leaf down was also wilted but the others were turgid. The twenty-fifth 

 day the apical part of the stem had shriveled and the disease was slowly passing downward. The vine 

 finally shriveled to the ground. 



(245.) Cucumber. There were no signs until the ninth day. Then the apex of the pricked leaf 

 was wilted. The following day the apical half of the leaf had changed to a dull, faintly yellowish green 

 and had wilted, the wilt clearly commencing in the pricked areas (see figure 74). The rest of the leaves 

 were normal. On the sixteenth day the blade of the pricked leaf was shriveled; the petiole was turgid 

 except toward the top where it was a trifle flabby. The upper five leaves were wilted and also the 



