Dec. io f 1913 
Disease of Sugar-Beet and Nasturtium Leaves 
191 
spots. Some of the inoculated leaves were taken to the laboratory, the 
black spots examined, and numerous bacteria found swarming in the 
cells. From these spots, produced by the first inoculations, the organ¬ 
ism was reisolated in pure culture, and sugar-beet leaves in the green¬ 
house were inoculated repeatedly, the dark spotting and streaking of the 
leaves occurring in every case. Altogether, more than 100 sugar-beet 
leaves were inoculated. Although the infection took readily at the 
inoculated places, the disease was not observed to occur on any uninocu¬ 
lated beet plants except in two instances, when several beets of a neigh¬ 
boring row became affected. No slugs or worms were on the leaves, but 
thrips were abundant, and there were also a number of grasshoppers 
which had escaped capture; so possibly the infection was carried by one 
of these insects. 
When the petioles, midrib, and large veins were inoculated by means 
of needle pricks, the infection took very rapidly, and the discoloration 
often ran along the course of the veins and veinlets. When the leaf 
blades were inoculated at the ends of tiny veins, there was only a dark¬ 
ened ring around the punctures. The infection took most rapidly on 
the petiole. (PI. XVII, fig. 1.) In three days after needle-prick inocula¬ 
tions in young growing leaves the tissue was depressed, darkened, and often 
ruptured for a distance of 5 mm. around the puncture. Young beet 
leaves with blades about 8 cm. in length very readily succumbed to 
needle-prick inoculation in the blade as well as in the petiole and mid¬ 
rib. When material from a young culture less than 2 days old was 
inoculated into rapidly growing leaves, the spotting began to show in 
24 hours. Old tissues were also found susceptible to the disease, but 
the infection did not take so rapidly. The sugar-beet root also was inocu¬ 
lated and the disease was found to take hold there slightly. (PI. XVII, 
fig. 2.) There was no soft-rot condition, but cavities occurred in the 
roots where the inoculation pricks were made. These cavities pene¬ 
trated into the interior of the beet and reached a depth of 2 cm. within 
two weeks after inoculation. Occasionally a cork-like condition of a 
dark color followed along the immediate line of the needle prick and no 
cavities were present. The discoloration, however, was not nearly so 
dark as in the leaf, nor was there as much tendency to spread as in the 
leaf. 
So far as the writers know, this organism has not been found in the 
field attacking the beet root, and as none of the field beets with affected 
leaves had any root trouble, it is thought that the disease in the field 
is confined strictly to the leaf. 
Spraying the organism on the leaves of beets did not produce the 
disease. Precautions were taken to prevent the bacteria from drying 
before they had time to get into the leaves. An infection cage was 
placed over beets growing in the open ground in the greenhouse, the 
