140 BOTANICAL GAZETTE [AUGUST 
or puncture of the fruit is necessary. This is further demonstrated 
by the number of infections occurring in apples. In some cases 
100 to 200 infections were found on single apples, and recently 
Scott's reports the enormous number of 1,000 to 1,200 infections 
on single fruits. It is not likely that these represent previous — 
mechanical injury to the fruits. 
APPRESSORIA IN RELATION TO DISSEMINATION. 
The behavior of the appressoria of the bitter-rot fungus under 
natural conditions is of interest from a biological standpoint. The 
spores of this fungus are imbedded in a gelatinous substance, which 
causes them to stick together in waxy masses when dry. By reason 
of this condition the spores cannot be distributed by wind. 50 
far as known they are entirely dependent for their dissemination 
upon rain, although it is probable that insects take an active part 
in carrying the spores from tree to tree. Each season the first ge™ 
eral infection of apples by the bitter rot is due to rain washing the 
spores from the limb cankers, in which the fungus hibernates, 1 
the apples below. This is plainly shown by the observation that 
on a tree the infected apples are distributed within an area that 
can be circumscribed by a cone having its apex at the canker, the 
source of infection. Furthermore, drops of rainwater, collected 
from badly infected trees, usually contain numerous spores of the 
bitter-rot fungus. é 
Since the rain, at least in many cases, is the chief factor in dis- 
tributing the bitter-rot spores, it is of interest to determine the effect 
of wetting and drying on the spores, and also the relative vitality 
of the spores and the appressoria. It should be stated, that while 
the spores are imbedded in their mucilaginous covering, they retain 
their vitality for a long time, but not during the entire winter, 
as has often been reported. In the latitude of Southern Tilinols, 
spores remaining on apples under the trees either germinate** seg 
perish long before spring. Spores taken from time to time from 
a diseased apple, which was kept dry in the laboratory from August 
until January, showed a large percentage of germination as late a> 
Nov. 29, but later rapidly lost their vitality. 
ott, W. M., The control of apple bitter rot.. U. S. Dept. Agr. Bu 
Industry Bull. 93. pls. 8. 1906. 
14 See also CLINTON, /. ¢. 
r. Pl 
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