WILT OF CUCURBITS. 249 



Clearly, therefore, Dr. Halsted's inoculations were not made with this organism. On 

 April 5, five of the tomato-plants were watered as follows: Two with 500 cc. 0.1 per cent 

 watery solution of KNO3, one with 500 cc. of 0.1 per cent watery solution of kainit, one 

 with 500 cc. 0.1 per cent watery solution of muriate of potash, and one with 500 cc. of 

 water allowed to stand, with shaking on 2 grams of fine, dissolved bone ash. Five days 

 later each plant was given another 500 cc. of the solution. There was no visible effect from 

 the previous waterings. Only the nitrate of potash seemed to show a doubtful trace on one 

 or two plants. There was nothing distinct and there was no change up to June 2 2 . 

 For the check-plants see the next series. 



Inoculations of March 19, 1895. 



Three cucumber-vines (Cucumis sativus) bearing 2 and 3 leaves were inoculated as 

 checks on the tomatoes and pears pricked on March 18. The remnant of the slant agar- 

 culture No. 3, March 13, was used for making the inoculations. A small, sharp, steel needle 

 was used to introduce the bacteria. 



(147.) Many pricks were made on one leaf. The third day, the vine rotted off at the base: It 

 had been kept too wet and was attacked by nematodes. 



(148.) Many pricks were made on one of the leaves. The sixth day at 9 a.m. there was no wilt 

 but at 10:30 a.m. there was the slightest trace of wilt at the apex of the inoculated leaf. There was 

 no change of color. The following morning half of the leaf-blade had wilted with a characteristic 

 change of color. Twenty-four hours later (eighth day) the whole of the pricked blade had wilted 

 except a small area near its base. The petiole was rigid. The tenth day there was a slight wilt of the 

 first leaf up and the first one down. The following morning the two leaves last mentioned showed a 

 decided wilt, the first one down being the more badly affected. The thirteenth day all the leaves 

 were wilted and the vine, which was a small one, was cut for examination. The vessels of the stem 

 were plugged by bacilli which were present in enormous numbers. They were also abundant in the 

 midrib and smaller veins of the partially developed second leaf above the pricked one. No motile 

 rods were observed in any of the sections, not even in those near the tip of the vine (specimens saved 

 in alcohol). 



(149.) Many pricks were made on one leaf. The fifth day (3 p.m.) there was no trace of the dis- 

 ease but the next morning the pricked leaf showed wilt at the apex. About one-fifth of the leaf was 

 affected. There was yet no change of color. Twenty-four hours later over half of the leaf-blade was 

 wilted with the characteristic change of color. The eighth day the whole of the pricked blade had 

 wilted with the exception of a small area near its base. The petiole was turgid. The following day 

 the first leaf on either side of the pricked one was slightly wilted. The eleventh day the blades of 

 these two leaves showed decided wilt, that of the lower one being the most wilted. The thirteenth 

 day all the leaves were wilted and the vine was cut for examination under the microscope. The 

 vessels of the stem were plugged by enormous numbers of bacilli even to the extreme tip (fig. 67). 



Remarks. This sufficiently settled the virulent nature of the bacteria pricked into 

 the pear-stems and tomato shoots out of this same pure culture the day before. We may, 

 therefore, conclude that pears and tomatoes are not affected by this organism. The micro- 

 scopic examination shows that bacteria are sometimes present in the veins of the leaf very 

 soon after it wilts, whether they are always present in advance of the wilt or whether the 

 secondary wilt is sometimes due entirely to occlusions of vessels in the stem or petiole 

 remains to be determined (see fig. 68). 



Inoculations of April 15, 1895. 



Muskmelons, cucumbers, squashes, pumpkins, watermelons and tomatoes were 

 inoculated in the hothouse at midday with bacilli (cucumber-strain) from a pure, motile, 

 slant agar-culture 48 hours old (tube 1, April 13, from agar stab No. 2, April 8). All the 

 inoculations were made by needle-pricks. The loop and needle were flamed and cooled 

 each time before using. 



A fresh mass of the slime was fished out of the tube for the inoculation of each plant 

 and the bacteria were pricked in immediately to avoid danger from drying. 



