May 2, X921 
A Bacterial Budrot of Cannas 
147 
work was therefore postponed until the following spring, when more 
favorable conditions would obtain. 
When the disease appeared in 1919, isolations were made from active 
young infections on leaves and petioles; and single colony subcultures 
from these were used for inoculating young vigorous cannas, obtained 
from a new source, in large pots in the hothouse. Suspensions from 
young agar cultures were sprayed into the youngest rolled leaf of some 
plants without wounding. In other cases the stalk below the lowest 
leaf blade was smeared with bacteria, and pricks were made through 
this to the young leaves within. Part of the inoculated plants of each 
lot were kept in cages and sprayed with sterile water for 36 hours; 
others were left in the open house. Controls in other cages were sprayed 
with sterile water. 
Good prompt infections were obtained by both spray and prick in¬ 
oculations on the plants that were kept in cages, and only fair infec¬ 
tions on those in the open house that were pricked. Controls remained 
healthy. Infection was apparent on the sprayed plants only when the 
young, susceptible leaves which were tightly rolled at the time of in¬ 
oculation emerged or unrolled, usually after six or seven days. On the 
oldest rolled leaves those spots which at this time showed as small 
stomatal infections did not progress further. On younger leaves the 
initial stomatal stage was past, the spots extending from vein to vein 
and beginning to lengthen into streaks (PI. 36, A). On pricked plants 
kept in cages, infection was more rapid and destructive, as is shown on 
Plate 36, B, C. Here infection showed on the fourth day, running down¬ 
ward from pricks seen in the photograph near the tips of the leaves 
(X, X). These leaves were tightly rolled when pricked through the 
enveloping folds of older leaves. In the leaf shown on Plate 36, C, 
the streak from the pricks on the midrib was 3 cm. long on the fourth 
day. One day later it was 10 cm. long, and by the eleventh day it had 
reached almost to the base of the next older leaf, widening downward 
where inclosed by the sheathing petioles and killing the shoot com¬ 
pletely. After the plants were once infected, secondary infections took 
place in some cases on young shoots which were in the same pots with 
inoculated shoots but which were too young at the time of inoculation to 
have been directly infected—that is, were without any leaf which had 
begun to unfold. Younger unfolding leaves on sprayed shoots also 
showed infection as they emerged some weeks later. 
From several of these infections reisolations were made, and inocula¬ 
tions with single colony transfers thus obtained gave typical infections 
on cannas when inoculated by spraying and by needle pricks. These 
isolations and reisolations were used for cultural work in comparison 
with cultures of J:he previous year, with which they were found to agree. 
36731°—21 - 3 
