224 BACTERIA IN RELATION TO PLANT DISEASES. 



lated September 1 6 from a smooth, wet-shining, gray- white culture on potato (No. i , Septem- 

 ber 8) . This potato culture was derived from the interior of a cucumber fruit. On Septem- 

 ber 13 it was described as forming on the potato slow-growing, flat, gray- white wet-shining 

 masses, which spun out in a fine thread when touched with a needle. The pricks were made 

 with a steel needle on one leaf -blade of each plant, except No. 17, which was pricked on the 

 center of the lamina of 2 leaves. 



(16.) The first signs appeared the fifth day after inoculation, at noon, and first in the infected 

 leaf. By 4 o'clock of the same day the disease had spread considerably and occupied about half of 

 the leaf, forming a wedge-shaped area from the pricked portion outward. The rest of the foliage was 

 normal. Theeighth day the blade of the infected leaf was wholly dried up exceptasmall area (iX i cm.) 

 at the tip of the petiole which was yet green but not turgid. The internode below was 12 cm. long. 

 The next node above had lost its leaf long since (killed by a tobacco- water spray). The distance 

 from the infected leaf to the second node above, which bore a good leaf, was 18 cm. Both of these 

 nearest leaves as well as more remote ones were perfectly normal on October 9 (the eight day) as was 

 also the upright petiole of the pricked leaf. There was no further visible change until October 1 2 . 

 Then the first leaf below the pricked one drooped on one side. The first leaf above was still turgid. 

 There was no change on October 13, 14, or 15. The last record of this plant was made on October 1 7. 

 At that time the first leaf above the infected one was also drooping but all the others were normal. 



(17.) The pricked leaves were well toward the extremity of the vine and were separated only by 

 one internode. The leaves were normal at noon on the sixth day, but the morning of the seventh day 

 both blades were drooping slightly and showed change of color. At 4 p. m. these signs were more 

 decided and involved the whole leaf-blade. The following morning (October 9) the blades of the 

 infected leaves were collapsed and had begun to shrivel. At 2 p. m. of the same day the nearest leaf 

 to either side of the infected ones (leaves which were perfectly turgid in the morning) began to show 

 unmistakable signs of the disease, i. e., one blade was drooping decidedly at the tip and the other on 

 one of the side lobes. The other leaves were perfectly healthy, and the petioles of the infected leaves 

 were still turgid. The temperature on this day was 60° to 70° F. On October 10, at 9 a. m., the leaf 

 next above the upper pricked one was drooping on both sides as well as at the tip and the next two 

 above were flabby. The leaf next below the lower pricked one was drooping at the tip, and on either 

 side. The second leaf below was still turgid, but by noon of the same day it was drooping. The 

 tenth day all the leaves above were wilted and also the four next below the lowest pricked leaf, 

 two additional ones having drooped that morning. The eleventh day the fifth leaf below the inocu- 

 lated ones was drooping. The three below this were still turgid and were the only sound leaves 

 remaining on the vine. The following day the fifth leaf down was wholly collapsed. The rest of the 

 wilted leaves had shriveled but were not yet dry-brittle. The three basal leaves were still normal. 

 The vine was now brought into the laboratory. On October 14 the stem had begun to shrivel in 

 places and the uppermost of the three basal leaves had drooped, leaving only two sound leaves on the 

 vine. Two days later all the leaves were wilted and the upper part of the stem was shriveled. 



(18.) The blade of a large healthy leaf near the tip of the vine was pricked. On the afternoon of 

 the seventh day the inoculated leaf was normal. The morning of the eight day a part of the pricked 

 leaf-blade had changed color and over half of it was wilted. By 2 p. m. of the same day it was wholly 

 wilted with exception of a square centimeter where the blade joined the petiole. The petiole was 

 turgid as was also the leaf to either side. The ninth day the pricked leaf was wholly soft-flabby, 

 drooping and beginning to dry. All the other leaves were turgid and remained so for some days. 

 The thirteenth day the leaf next above and the one next below the inoculated leaf were slightly 

 flabby. Bacteria were now present in the vessels of the fruit. On October 15 the leaf to each side 

 of the inoculated one showed decided wilt. Two-thirds of each blade hung flaccid. The rest of the 

 vine was normal, including all of the petioles. The diseased leaves were now removed and put into 

 alcohol. On the sixteenth day none of the leaves remaining on the vine showed any signs of wilt. 

 Sections from all parts were removed and put into alcohol (fig. 59). 



Inoculations of Oct. 25. 1894 (noon). 



Three young vines of Cucumis saiivus, were sprayed thoroughly with a mixture which 

 was three-fourths sterile water and one-fourth a potato-broth-culture of Bacillus trachei- 

 philus 2 days old (tube 8, October 23). These plants were placed under bell-jars in order 

 that they might be kept free from aphides which I suspected might be the means of intro- 

 ducing the bacteria into the plant. Upon a fourth cucumber vine which was sprayed in like 

 manner, numerous aphides {Aphis gossypii) were colonized, and the vine placed under a 



