APPLE DISEASES 67 
found on the woody parts of the apple, and then only on very 
susceptible varieties. Later in the summer small, greenish, 
spherical enlargements of the leaf may be observed on the cedar. 
Very soon these take on their final shape, which in some cases 
is reniform (Fig. IS). The 
enlargements or galls con- 
tinue their growth, becom- 
ing brown and _ attaining 
a diameter of two inches 
or less by the end of the 
season. During the late 
autumn and early spring, 
these galls, or cedar-apples 
as they are called, show 
numerous depressions over 
their surfaces (Fig. 18) and 
in early spring a brown 
horn projects for an inch 
or more from each depres- 
sion (Fig. 19). In rainy 
weather these horns _be- Fic. 19. — Cedar-apples in spring condi- 
come gelatinous and tions. Note the horns. 
orange-colored. When 
thus fully formed the cedar-apple resembles a flower, whence 
the popular name cedar-flowers. 
Cause of apple-rust. - 
The apple-rust pathogene is a fungus, Gymnosporangium 
Juniperi-virginiane, with a complex life-history as well as a 
long name. (The apple-rust fungus common in New England 
is Gymnosporangium globosum Farlow. This species occurs 
also on pear; see page 341.) Fortunately, however, the cycle 
of the parasite is well known to botanists and to many apple- 
growers. The fungus was first found and described on the 
red cedar, but no suspicion of its connection. with the apple 
