Mar. 19, 1917 
Dissemination of Angular Leaf spot of Cotton 
467 
increase of diseased leaves. At the time two control plants standing 
next to inoculated plants were also diseased. Thus, there is without 
doubt a rapid increase of the number of the spots on infected plants 
and those adjacent, probably due, as Rolfs (1915, a) points out, to the 
spread of the bacteria by contact with uninfected leaves and plants in 
the presence of sufficient moisture. 
During the observations made on June 26, to note the spread of the 
disease in this field, it was found that the row on each side of that in¬ 
oculated contained infected plants, though the disease appeared to be 
spread farther toward the east than the west. That part of the field 
was carefully diagramed, an accurate record made of the disease on each 
plant, and the data then charted for closer study. The chart is repro¬ 
duced here to show the true situation in the field at that time (fig. 1, B.) 
All the plants are represented by cross marks, those originally inocu¬ 
lated with Bacterium malvacearum are divided into series, each series 
being given the number of our culture used. The numbers near the 
plants of the neighboring rows and of the checks designate the number 
of angular leaf spots found on them on June 27 and 28. The inoculated 
plants were so badly diseased as to make such data useless. 
Two facts stand out upon examination of the chart: (1) There had 
been very little spread of the disease in a westerly direction as contrasted 
with that toward the east, and (2) the spread toward the east was strik¬ 
ingly opposite the inoculated plants as compared to the control plants. 
Upon closer study of these points it will be noticed that one had to pro¬ 
ceed 14 rows to the east to find a row comparable in amount of disease 
with the second one west of the inoculated row. Further, a decrease in 
disease is noticed west of wide skips in the inoculated row almost as 
pronounced as that west of the control plants. 
The significance of these data was much of a surprise to the author; 
therefore, he immediately set about to duplicate the original conditions, 
hoping at least to obtain some partial repetition of these results. A row 
in the same field, 35 rows west of the first inoculated row, was chosen for 
the second experiment. For this inoculation a bacterial suspension was 
made by grinding a large number of badly spotted leaves in a food chop¬ 
per and diluting the macerated tissue with water. The rapid spread of 
the disease after the first inoculation led the author to believe that the 
bacteria in culture had been more or less attenuated, since it was eight 
days after inoculation before the disease appeared on the leaves. Unless 
a great amount of this spread had taken place at one time, it would have 
been difficult to understand how the disease could progress so far in one 
direction if each spot took 8 to 10 days to appear. 
In the row used, a number of plants serving as controls were not 
inoculated, a number were inoculated, and others again left as controls. 
A shallow dish of the fresh suspension of bacteria was held in one hand 
while each of the leaves of the plants to be inoculated was immersed; 
