254 BACTERIA IN RELATION TO PLANT DISEASES. 



Inoculations of May 13, 1895. 



Nineteen potato-vines were inoculated in the hothouse with B. tracheiphilus (cucumber- 

 strain) the virulence of which was checked by inoculation into five cucumbers. The pota- 

 toes were planted in 7 -inch pots April 23. Large tubers were halved and all but two eyes 

 cut out. At the time of inoculation each pot bore five or six shoots 8 to 10 inches high, 

 growing rapidly and all very thrifty. The cucumbers {Cucumis sativus) were several months 

 old, 2 to 3 feet high and in bloom. The bacteria used for inoculation were from a pure slant 

 agar-culture (tube i. May 11) made for this purpose from a glycerin-agar-culture (No. 8, 

 May I , reinoculated May 8) . The growth was a characteristic, smooth, wet-shining, milk- 

 white streak, much more sticky than the glycerine-agar-culture from which it was made. 

 The weather was cool. The temperature in the hothouse at the time of inoculation was 

 80° F. All the pricks made were deep. The needle and loop were flamed and cooled each 

 time and thousands of living bacteria were thrust in. The potatoes received many pricks 

 into young leaves and tender shoots. 



(171 to 189.) Potato (Solanum tuberosum). No result. 



(190.) Cucumber. The inoculation was made in a leaf borne on the tenth node (there were many 

 nodes above). Many pricks were made near the midrib about half-way from the base of the blade 

 to the tip. The blade was about 5 inches broad. Up to i p.m. May 27 (end of the fourteenth day) 

 there was no trace of the disease, but at 5 p.m. of that day a very small area (less than one square 

 centimeter) was wilted. The eighteenth day no constitutional signs had appeared — only wilt and 

 shriveling of the pricked leaf-blade. Half of the latter was dry-shriveled and the rest hung flabby. 

 There was no wilt above or below this leaf. Twenty-one days after the inoculation the pricked blade 

 was wholly dry-shriveled and of a brownish color. The petiole was green and turgid except the 

 upper inch which had become slightly yellowish and a little flabby. The leaves above and below were 

 normal. Three days later there was still no wilt of the leaves above or below. The tip of the petiole 

 of the pricked leaf was flabby. On the beginning of the twenty-fifth day the first secondary wilt 

 appeared. This was in the first two leaves above the pricked one. The rest of the leaves were turgid. 

 The general infection of the plant was very slow. June 8th (26 days after inoculation) the blade of 

 the first leaf below the pricked one showed wilt (9 a.m.). At noon the blade of the third leaf up and 

 of the second leaf down were wilted and that of the first leaf up had dry-shriveled the same as the 

 pricked leaf. June 15 the vine had lost all its leaves by the wilt but the stem was yet green and turgid. 

 A petiole was now cut across and the sticky bacterial ooze was pricked into the leaves and stems of 

 pumpkin and squash. (No. 198 and others.) The same day the vine was cut and put into 75 per 

 cent alcohol for microtome sections. It was not then examined microscopically but has been since — 

 enormous numbers of bacteria being found in the vascular bundles of the stem. 



(191.) Cucumber. Many pricks were made in the middle of a leaf-blade (5 inches broad) to 

 one side of the midrib. The pricked leaf was on the tenth node. The sixth day (2.30 p.m.) the leaf 

 had wilted over an area of 1X3 cm. from the pricks outward, along both sides of a main vein nearly 

 to the margin of the leaf. There was no wilt the preceding day at 4 p.m. The seventh day there was 

 little change. Twenty-five hours later the bulk of the leaf was still turgid. The ninth day the whole 

 leaf-blade drooped and the pricked side was drying out. Two days later the whole blade of the oricked 

 leaf had shriveled. The petiole was still green and rigid. In the afternoon of the eleventh day the 

 blade of the first leaf up began to droop decidedly on one side. The following morning it had partly 

 recovered its turgor. At 2 p.m. the leaf-blade hung down flabby. The fourteenth day the blades 

 of the first, second and third leaves up had collapsed and also those of the first and second down. 

 The petiole of the pricked leaf was beginning to shrivel in the upper two inches. Four days later 

 the leaf-blades were all down. The petiole of the pricked leaf had shriveled nearly to the base. 

 The petioles below were turgid but those above were beginning to be flabby. 



(192.) Cucumber. Many pricks were made in the middle apical part of a leaf -blade about 4.5 

 inches broad. The leaf was on the eleventh node. The sixth day (2' 30" p.m.) the leaf had wilted 

 from the pricked part to the apex, a length of 4 cm. and a breadth of about i cm. The foUowing 

 morning there was little change. The eighth day the bulk of the leaf was still turgid. The day was 

 cool, cloudy, and rainy. The following day about half of the blade of the pricked leaf had wilted. 

 The petiole was rigid. The eleventh day the whole blade of the pricked leaf had shriveled. The 

 petiole was still green and rigid. Twenty-four hours later the petiole of the leaf was still normal 

 externally as was also the first leaf to either side of the pricked one. Four hours later the blade of the 

 first leaf up had wilted. The fourteenth day the blades of the first and second leaves down collapsed. 



