WILT OF CUCURBITS. 275 



Possibly the plants may have been very resistant but my opinion at the time was that 

 the bacteria were dead when inoculated. This is possible since the tube was inoculated 

 very' copiously on the start (by means of a pipette) and would consequently convert the 

 sugar of the potato into a harmful acid sooner than under ordinary circumstances. Prob- 

 ably the viscid bacteria on that part of the potato exposed to the air were still living, and 

 very likely the experiment would have succeeded had slime been taken from the exposed 

 surface, or had the latter been washed down into the fluid at the bottom of the tube by 

 prolonged shaking, as in the experiment of July 16. The previous freezing had nothing to 

 do with it, since freezing does not destroy the pathogenic properties of the organism (see 

 experiment of July 16). 



Inoculations op July 15, 1896. 



A second set of inoculations was made in the hothouse to determine whether the disease 

 could be cut out. The plants used were small muskmelons {Cucumis melo) and all the pricks 

 were made on the apical part of the blade of the first or second leaf above the cotyledons. 

 Many delicate pricks were made, covering an area not to exceed one square centimeter. 

 My method of inoculation was to heat a platinum loop to redness, wait until cool, open the 

 tube containing the culture and take out a loop of fluid from the bottom. I placed this loop 

 of fluid on the leaf and pricked through it with a steel needle which was heated and cooled 

 each time. The fluid was then spread so as to cover fully the pricked area in case any 

 pricks extended outside of the liquid. The pricked portion was then covered from the 

 direct rays of the sun for some hours. The infectious material used for these inoculations 

 was taken from potato culture No. 12, July 8, i. e., the same culture which was used for 

 the inoculations of the preceding day. 



(335 to 354.) Twenty muskmelons. 

 No result. 



Remarks. — The melons were all of one variety — Princess. It was my intention to cut 

 away the leaves close to the stem as soon as wilt appeared, but the experiment failed, the 

 plants being inoculated from the same part of the same tube as the preceding. It is a 

 good illustration of the danger of putting all one's eggs into a single basket. Merely as an 

 ordinary precaution this set ought to have been inoculated from a different culture and 

 transfers should have been made from each one into nutrient agar just prior to the inocula- 

 tions so as to know whether the bacteria were really alive. Examination in a hanging drop 

 just prior to inoculation would also have shown whether the fluid contained motile rods 

 suitable for inoculation. As it was, two otherwise carefully planned experiments yielded 

 only negative and disappointing results — ^results which have considerable interest, however, 

 when compared with those of the next series. 



Inoculations op July 16, 1896. 



A third set of inoculations (i^ to 5^ 30" p. m.) was made to see if the disease could 

 be cut out. The plants were in a hothouse and the bacteria used were from tube 1 1 , July 8 

 (a potato culture made from the bouillon culture which had been cooled to — 77° C.) . This 

 culture was made at the same time and from the same tube as culture No. 12, July 8 (see 

 inoculations of July 14, and 15 which failed). Loops of the liquid were also taken from the 

 bottom of the tube but only after it had been shaken thoroughly in order to wash the sticky 

 bacteria off the cylinder into the liquid. This was the only particular in which the material 

 used for inoculation varied from that used for the preceding experiments which failed. 

 Well-developed young, healthy, and rapidly growing cucumber plants {Cucumis sativus) 

 were inoculated. The variety selected was White Wonder. Many delicate pricks (40 to 

 70) were made in the apical part of one leaf-blade of each plant, covering an area of not 

 more than i sq. cm. The pricks themselves did the plant no injury. The platinum loop 

 and the steel needle used in the operation were flamed and cooled each time before using. 



