APPLE DISEASES 19 
inoculation spots an inch in diameter will develop on the fruits ; 
however, the rate of rotting depends on the temperature and 
the age and variety of the fruit concerned. As previously 
pointed out, the fungus develops fruiting pustules, acervuli, 
by the time the spot is an inch or less in diameter. Their 
general appearance and arrangement has also been described. 
Within the acervuli conidiophores arise, each stalk being capable 
of developing several conidia successively at the free outer end. 
These spores, as they are formed, pile up at the apex of the 
acervulus and in quantities are pink. These groups of conidia 
in the concentric or scattered acervuli produce a very striking 
appearance, which forms one of the most characteristic symp- 
toms of the disease. When moist the conidia cohere in sticky 
masses for a time, but when wet are easily separated and washed 
to other points during the rains. Such conidia are in turn 
capable of inducing bitter-rot and within three to seven days 
another crop of conidia is ready for dissemination. This 
process may be frequently repeated from June to October, if 
weather conditions are favorable. Many of the conidia are 
carried in rain drops by heavy winds to other apple-trees 
which thus become new centers of infection. Many conidia, 
too, are deposited on dead parts ofa tree and there germinate, 
and establish the fungus for the winter. Accordingly it has 
been shown that the pathogene not only hibernates in the 
bitter-rot mummies and cankers, but also in the Illinois blister- 
cankers, dead tips of fruit-spurs, frost-injured portions of 
limbs, fire-blight cankers, blotch and black-rot cankers. In 
any or all of these places the fungus overwinters in the form 
of mycelium. In the spring, the parasite resumes activities 
by developing acervuli from which the first spring crop of 
conidia are produced. The fungus has a sexual stage, in 
which perithecia, asci and ascospores are borne, but it has not 
been shown that this stage is important in the life-cycle of 
the organism. 
