WILT OF CUCURBITS. 225 
bell-jar. The first three vines were used as checks on the behavior of the fourth. The air 
under the bell-jars was quite moist and at 4 p.m. water stood in tiny beads on the margin of 
the leaves. At the end of 24 hours the under surface of the sprayed leaves was still wet in 
places especially that of the leaf on which the aphides were colonized. Some of the latter 
had migrated to other leaves. All were sucking the plant juices and for fear of mechanical 
injury I brushed off and destroyed most of them. None were observed on the check vines. 
The bell-jars were removed and the plants exposed to the air for half an hour to dry off a 
little and then the jars were put back. This 
was done frequently during the experiment. 
The fourth day the vines were still healthy 
and the checks were free from aphides. 
Tube 8, October 23, was inoculated from 
a very sticky potato culture (tube 8, October 
17), which was inoculated from a single, small, 
white colony on a slant agar culture streaked 
September 27 fromtube1, September 17, which 
was inoculated from the interior of plant No. 2. 
(20.) Cucumber (check). Plant about 5 
inches high with two well-developed leaves and 
one more coming, also two green cotyledons. 
The bacterial fluid was sprayed on the under sur- 
face of the two largest leaves and the plant was 
then put back under the bell-jar. The eight day vn , 
after spraying, this vine was still healthy. It had 
grown an inch or two since October 25. It was 
still free from ants and aphides. Two days later 
it was healthy and growing rapidly. The twenty- 
third day the bell-jar was removed and not re- 
placed as the plant was beginning to be spindling 
although no trace of the disease had appeared. 
The thirty-fourth day the vine was still free from 
the disease but had remained spindling since the 
removal of the bell-jar. By the fifty-first day 
the plant had lost all its leaves and the tip of the 
stem had wilted. It was not much over 1 foot 
high, having never recovered from the stunting 
due to keeping it under the bell-jar. Thin sections oe 2 
were cut and a microscopic examination made, Em Oz. S 
but no bacteria were found in the vessels. 
(21.) Cucumber (check). This plant was the OY 
same size as No. 20. It had two green cotyledons, 
bore one well-developed leaf, which was sprayed 
on its under surface, one twisted deformed leaf, 
and two undeveloped leaves. After spraying ‘ 
it was placed at once under the bell-jar. The Fig. 59." 
eighth day this vine resembled the preceding in all 
particulars. It remained healthy and grew rapidly for a time but on the final removal of the bell-jar 
(the twenty-third day) it was beginning to be spindling although free from the disease. The thirty- 
fourth day it was still free from wilt but had remained spindling. The forty-sixth day it was brought 
into the laboratory and examined for the presence of the bacillus in its tissues. It had never recovered 
from the stunting due to keeping it under the bell-jar. Since the removal of the latter it had also 
suffered to some extent from mildew, from aphides, and on two or three occasions from insufficient 
moisture. It was not over 12 inches high. For the 3 weeks preceding it had been losing its foliage 
*Fic. 59.—Cucumber No. 18, inoculated at « by needle-pricks with a pure culture of Bacillus tracheiphilus on Oct. 
1, 1894. Numbered parts were removed and fixed in alcohol Oct. 16. They were subsequently embedded in paraffin, 
sectioned and stained for presence of bacteria, which were found in vessels at all points marked +, and not at those 
marked —. They occurred in greater or less numbers according to distance from inoculated leaf, or from main axis. 
Exclusive of wilt there were no surface indications of disease. About one-fourth natural size. 
