INFECTION THROUGH STOMATA. 61 
the ordinary stomata (vol. I, figs. 74 and 75), the subject will be treated under this head, 
although it is considered probable that the other form of infection also occurs. In any 
event, the copious functioning of the water-pores must contribute very materially to the 
certainty of stomatal infection. 
In 1902 the writer studied this disease on Long Island, where it is prevalent, and 
brought back pure cultures, the earlier ones received from 
Mr. Stewart having been allowed to die. The infections 
were obtained with various subcultures made from these 
original cultures. The plants were inoculated in the seed- 
ling-stage, the material for infection being obtained from 
cultures on slant agar. The inoculations were made by 
placing a small quantity of the bacterial slime on the tips 
of sweet-corn leaves which were extruding drops of water 
(vol. I, fig. 73). This was done in the afternoon, generally 
toward sunset, the plants, which were in small pots, being 
well watered and placed under the greenhouse bench to 
protect from the bactericidal action of light. After a day 
or two they were taken out of the shade and placed on 
the bench. They grew rapidly, and after some weeks, 
during which time they were repotted once or twice, they 
were planted out on one of the Department of Agriculture 
farms. They were well cultivated, experienced no setback 
by being transplanted to the open, and those which were 
not dwarfed by the early appearance of the disease grew 
satisfactorily. The first signs of the disease were at the 
tips of the inoculated leaves, and on some of the plants they 
appeared within a week. The first cases—that is, plants 
showing secondary or general signs appeared in about 3 
weeks, but not many developed so soon, most appearing 
after 9 weeks. Cases to the number of several hundred 
continued to appear until frost put an end to the experi- 
ment about 3 months from the time of planting. These 
plants were several feet high when the general or constitu- 
tional signs first appeared. A macroscopic examination of 
all of these cases and a microscopic examination of a con- 
siderable number of them showed that the first parts of the 
stem to be infected were the basal nodes, 7. e., those which 
gave rise to the inoculated leaves. The organism finally 
occupied the vascular system quite fully, filling the bundles 
in many cases from the base of the stem to the male inflo- 
rescence, a distance of 3 to 4 feet, and also passing out into 
the bundles of the large middle and upper leaves, but 
usually not reaching the surface of any part of the plant, 
so far as observed, except on the inner surface of certain 
leaf-sheaths and on some of the inner husks of the ears Fig. 14.* 
(fig. 14). 
The spot disease of Delphinium (vol. I, fig. 127) is another malady in which infection 
takes place readily through the unbroken leaf-surface and stem-surface, 7. e., through 
*Fic. 14.—Inner husk of sweet corn, showing yellow spots and water-soaked areas in parenchyma, due to Bacter- 
ium stewarti. In places also bacteria were oozing to inner surface. The bundles were occupied by thebacteria. From 
U. S. Dept. of Agriculture farm on the Flats below the Washington monument. Plant inoculated in seedling stage. 
Photographed Oct. 21, 1902. Movement of organisms was from young leaves downward into base of stem and thence 
slowly upward through vascular bundles of stem into ear, over 2}4 months meanwhile having elapsed. Natural size. 
