= FH - — 7 “ — _ “ i 
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 atthe 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 OF 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, 7. 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 isa 
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 OF JULY 16, 1896. 
A third set of inoculations (1" 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 11, 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 1 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. 
