240 BACTERIA IN RELATION TO PLANT DISEASES. 



disappeared from the cells, not from all, however, as I should have supposed. The roots bore live- 

 small healthy tubers which seemed to be mature. The largest was 1 inch in diameter and the smallest 

 0.25 inch. In view of these facts the probabilities are that the plant had simply reached maturity, 

 performed its function, and was dying naturally. Its early maturity was induced by the smallness 

 of the pot. This explanation is the more probable from the fact that the roots had not made any 

 attempt to occupy the new soil of the larger pot to which the vine was transplanted. 



(64.) Potato. Two shoots, 6 and 12 inches high, were pricked, one on the stem, the other on two 

 leaves. There was no result from the inoculation. The vine grew rapidly for a time, then the leaves 

 began to yellow and shrivel from the top down, and by the forty-first day the upper part of the stem 

 had shriveled also. Sections of the stem of the pricked shoot showed no bacteria. The earth was 

 washed from the roots which were then examined. There were three small, mature tubers. The 

 old one had not rotted. 



(65.) Potato. Two shoots of this vine were pricked many times, one inoculation well-down on 

 the stem, the other on 2 leaves. The shoots were 10 and 12 inches high. The plant grew rapidly for 

 a time and then began to show signs of disease. The thirty-ninth day it had lost nearly all its leaves 

 and the upper 6 inches of the stem had shriveled. Sections were made from the base of the stem and 

 from the upper part close to the shriveled portion, which was far away from the point of inoculation, 

 but no bacteria or fungi were found. 



(66.) Potato. The plant bore four shoots, three 8 inches, one 10 inches high. Two shoots were 

 inoculated. The tallest shoot was pricked on 2 leaves, and the other on the stem. After a compara- 

 tively short period of rapid growth, the leaves began to yellow and shrivel from the top down and finally 

 the upper 8 inches of the stem shriveled (after 41 days). Sections of the pricked stem made below and 

 at various places above and in the pricked portion were examined under the microscope critically. No 

 fungi or bacteria were present or at least none were sufficiently abundant to be detected in unstained 

 sections. The other stems in the same pot were equally affected. One of these was not inoculated 

 at all. Clearly the change was not due to the insertion of Bacillus tracheiphilus. On washing away 

 the earth from the roots the cause of the decline was evident. The plant had matured five small 

 tubers and finished its life work. The old tuber was not rotten. 



(67 a and b, 68, 69 a, b, 70) Tomato {Lycopersicum esculenlum). These 6 plants were 6 to 8 

 inches high. Each was given many pricks, some in one leaf, others in the stem. There was no result 

 from the inoculations. 



(71, 72.) Muskmelon var. Miller's Cream (Cucumis melo). These vines were 3 inches high. 

 One leaf on each was pricked many times. No result. 



(73, 74) Muskmelon var. Extra Early Hackensack. Same size as preceding. One leaf of each 

 vine was pricked many times. No result. 



(75.) Muskmelon var. Extra Early Hackensack. One leaf of this vine was pricked. The 

 eighth day there were slight indications of wilt at the tip of the pricked leaf. Twenty-four hours 

 later half of the pricked leaf was flabby and hanging down. The twelfth day the first and second 

 leaves above the pricked one had collapsed. The plant was not over 3 to 4 inches high. The follow- 

 ing morning the vine was wilted. It was brought into the laboratory and examined under the 

 microscope. Bacilli were present in the interior of the plant in large numbers. Material was pre- 

 served in alcohol. 



(76.) Muskmelon var. Extra Early Hackensack. One leaf was pricked. No result. 



(77.) Muskmelon var. Extra Early Hackensack. A small plant like 75. One of the leaves 

 of this vine was pricked. The seventh day after inoculation an irregular wilt spot (about 0.5 sq.cm.) 

 had appeared on the side of the leaf toward the apex and within the pricked area. Two hours later 

 it had spread considerably and now involved about a dozen pricks. The ninth day the whole of 

 the pricked leaf was flabby and hung down, also the next leaf above. (The vine was small and these 

 two leaves were close together.) The twelfth day the pricked leaf, the first leaf above, and the tip 

 of the vine were wholly shriveled. The following morning the whole vine was wilted. It was brought 

 into the laboratory and examined microscopically. Large numbers of bacilli were found in the 

 bundles, some of which were actively motile. Material was preserved in alcohol. 



(78.) Winter Squash var. Hubbard {Cucurbita sp.). A leaf 3 inches broad was pricked many 

 times at the apex. Nearly 2 months after inoculation (January 25) when the last leaf had shriveled 

 the vine was brought into the laboratory and examined. The plant was stunted by being in the 

 same pot with a larger vine. Aphides and mildew had begun to attack it. There was no trace of 

 bacteria in the vessels or parenchyma of the stem. 



(79.) Winter Squash var. Hubbard. The apex of a leaf 3 inches broad was pricked. This vine 

 proved very resistant for a time but finally began to shrivel. On February 27 it was wholly dried out. 

 It was not observed very carefully during the two or three weeks immediately preceding this date. 

 1'his vine was now brought into the laboratory and examined microscopically. The vessels of one 



