234 BACTERIA IN RELATION TO PLANT DISEASES. 



more introduced into the insect-cage. They were taken out at 3'' 30'" p.m. but not until I had seen 

 several of them insert their beaks always into the veins. The second day the vines were beautifully 

 thrifty. Small diaphanous spots 2 mm. in diameter had appeared on several leaves. November 28, 

 there was no trace of wilt. The twenty-seventh day one of the vines looked suspicious but no un- 

 mistakable signs of wilt appeared until the morning of the thirty-eighth day. Then one small leaf 

 was wholly collapsed and part of its petiole hung flabby. The color and general appearance suggested 

 the bacterial blight. Above and below this wilted leaf were turgid bright green healthy leaves. Three 

 days later no additional leaves had wilted. If this plant was examined under the microscope records 

 do not show. 



(35 a and b.) A pot containing 2 vines about 8 inches high was placed under a big bell-jar. At 

 3 p.m. the leaves were atomized on both sides with the bacterial fluid and half a dozen squash bugs 

 were turned loose under the bell-jar. The next morning the bugs were all on the pot, none on the 

 vine. The second day the bugs were rather sluggish and not feeding much. They were removed 

 the morning of the third day. The twenty-fifth day one leaf on 35a was freshly wilted and another 

 small one was found shriveled down into the petiole and so must have become flabby some days before. 

 Possibly this is the leaf referred to on November 9, as showing a tiny trace of wilt on one side of the 

 lamina and of which there is no intermediate record. By the next morning the whole tip had wilted 

 and hung flabby. Below was one good turgid leaf. The vine was small and had no other leaves. 

 The following afternoon the last turgid leaf had wilted. The vine was now removed and brought 

 in for microscopic examination. The vessels in the middle part of the stem were found to be full 

 of the bacillus. In the hypocotyl, below the last wilted leaf, part of the vessels were still free from 

 infection and in the others a portion of the bacteria were plainly motile. On the twenty-sixth day 

 vine 356 was still normal. Nine days later (thirty-fifth day), a small leaf (about the third or fourth 

 from the tip), which had been collapsing for some days, was wholly shriveled. The leaves above it 

 were slightly flabby but as the plant had suffered considerably from mildew, aphides, and lack of 

 water, I was uncertain how to interpret the phenomenon. I watered the pot well and awaited develop- 

 ments. The next morning 1 leaf below and 3 above had wilted, although the soil was moist enough. 

 The plant was brought in and sections were made in various places. The vessels were found full of 

 the bacillus and some of the rods were actively motile. In the vicinity of the first leaf to wilt the 

 parenchyma of the stem also contained the bacillus, farther away the bacillus was sharply restricted 

 to the vessels and in the hypocotyl even these tissues were free from it. Assuming the first signs to 

 have appeared on December 3, the period of incubation was 3 1 days. The vine never recovered from 

 the stunting due to keeping it under the bell-jar. 



(36 a and b.) A pot containing two vines, 4 and 6 inches high, was placed under a bell-jar. It 

 was sprayed like the preceding and half a dozen squash-bugs were turned loose upon it. The following 

 morning the bugs were on the stem and ground and were not feeding. This was also true the second 

 day. The bugs appeared to be sluggish. The twenty-sixth day the vines showed no signs of the dis- 

 ease. The thirty-fifth day, 36a which was very small and had been languishing for weeks, partly on 

 account of the attacks of aphides, was quite dry with the exception of the base of the stem. The 

 stem was now examined microscopically but no bacteria were found. On the thirty-fifth day 366 

 had a small leaf (about the third or fourth from the tip) which was wholly shriveled. It had been 

 collapsing for some days. The leaves above it were slightly flabby, due perhaps to lack of water. 

 Three days later vine 366 was badly shriveled with the exception of the hypocotyl and one or two 

 of the first internodes. It was a small vine, never having recovered from its long sojourn under the 

 bell-jar. It was brought in and examined microscopically. In the third internode above the hypo- 

 cotyl the bacillus was abundant in a number of the bundles but motility was doubtful. In the first 

 internode above the hypocotyl the vessels of one bundle contained plenty of the bacillus but they 

 were not so closely packed as farther up and a part of the rods were plainly motile. No bacteria were 

 observed in any part of the hypocotyl. 



(37 0,6, and f. ) Three pots containing 3 vines, 7 to 9 inches high, with 12 good leaves besides the 

 cotyledons, were placed in an insect-cage into which 8 infected cucumber-beetles {Diabrotica 12- 

 punctala) were introduced at 1 p.m. The latter were very active, flying away from the vines imme- 

 diately to the top of the cage. The next morning the vines had sustained no injury. All the beetles 

 had disappeared except three which lay dead on the ground and were being eaten by ants. Twenty 

 striped cucumber-beetles {Diabrotica vittata) were now fed for half an hour on squash-fruit freshly 

 sprayed with Bacillus tracheiphilus and put into this cage at 10 a. m. Half of them were removed at 

 3.30 p.m. and the rest were removed the next morning. Two of the 3 vines had been gnawed a little. 

 All were beautifully thrifty. The twentieth day the inoculations were repeated using Diabrotica 

 vittata which had been kept alive on squash-fruits for this purpose. These had been transferred to 

 clean cut squash-fruits in clean covered dishes. (The old squash was moldy and rotten and mixed 

 with dirt.) On them I sprayed at 11 a.m. the contents of a pure potato-broth-culture (tube 2, 



