256 BACTERIA IN RELATION TO PLANT DISEASES. 
specimens of Diabrotica vittata were turned loose on them after the insects had been thoroughly 
sprayed with the dilute broth and left to crawl about in the infected liquid half an hour. Many of 
the leaves were already whitish on the margins and there were brown spots on the others and some 
mildew (Erysiphe chicoracearum). July 16. ‘The experiment failed. 
(196 a to g.) Cucumbers. Three pots containing seven plants much like those just described 
were placed in an insect-cage. The lower leaves were injured more than the preceding and there were 
large dead patches on the margins of some of the leaves and others were becoming whitish probably 
from malnutrition. The soil outside and in was thoroughly wet down and the wire of the cage was 
also wet so as to keep the air inside moist for the next 24 hours. The surface soil of the pots was then 
slightly sprayed with the dilute broth and also, thoroughly, every part of each plant—stems, young 
fruits, open flowers, old and young leaves (both sides), and the buds and leaf axils, so to as cause the 
disease if possible. The infectious material was from the same tube as that used for 195. Almost all 
the aphides were removed but not quite all. The broth used for infection was not very satisfactory. 
It was not swarming with rods, 7. e., therewas only here and there one in the hanging drop although 
of course where so much fluid was sprayed on, the aggregate number of rods was large. The inocu- 
lations were made on a cloudy, cool, rather damp afternoon. The plants in this cage were to be held 
as a check on the preceding. July 16. There was no result from the inoculation. 
INOCULATIONS OF JUNE 15, 1895. 
Squash-vines (Cucurbita sp.) and pumpkin-vines (Cucurbita pepo) were pricked and 
inoculated at noon with sticky bacterial ooze directly from the interior of a petiole of the 
inoculated cucumber-vine 190. Two cucumbers (Cucumis 
0 Ode sativus) were inoculated as checks. The day was sunny 
0 ar} O and hot. There is no statement as to the number of needle- 
s PQ 0) punctures, but only that the checks were inoculated in the 
2 a bem. —* O same way as the others. 
Y — 9 0 (197.) Cucumber. This vine was inoculated asa check. No 
(\ 0 Wy) 0 record of where inoculated but undoubtedly on some leaf-blade. 
0 a The fourteenth day (noon) half of the foliage had collapsed. Two 
days later the vine was brought into the laboratory and examined. 
O 0 From the cut end of the stem there oozed a sticky white bacterial 
slime, drawing out in slender threads, and a microscopic exami- 
Fig. 70.* nation showed that the vessels contained great numbers of a 
bacillus morphologically like B. tracheiphilus. 
(198.) Squash. Two terminal small leaves were pricked. 
No result. 
(199.) Cucumber. This vine was also inoculated as a check. On July 9 some of the leaves were 
wilted. It was brought in and examined microscopically. The vessels were found to be full of 
bacilli of variable size (fig. 70.) 
(200.) Squash. The third leaf from the tip was pricked and inoculated. 
No result. 
(201.) Pumpkin. The stem was pricked. 
No result. 
(202.) Pumpkin. The stem was pricked. 
No result. 
(203.) Squash. The stem was pricked. 
No result. 
(204.) Pumpkin. A leaf was inoculated. 
No result. 
Remarks.—The squash-plants and pumpkin-plants were kept under observation for 
38 days. The squashes were grown from seeds planted March 12. Here again cucumbers 
contracted the disease while squashes and pumpkins resisted it. 
*Fic. 70.—Bacteria, especially aberrant forms, from interior of cucumber-vine No. 199, inoculated with B. 
tracheiphilus. The common forms are 1.8 to 2.5 by 0.6 too.74. About 1 : rooo or r : 2000 is much larger, but transition 
forms were observed. Rarely one with a distinct capsule was seen. Cover-glass preparation stained by van 
Ermengem’s nitrate of silver method. July, 1895. 
ee 
