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 

 isreniform (Fig. 18). 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 

 s?ason. 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- 

 come gelatinous and 

 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-virginiance, 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 



FIG. 19. Cedar-apples in spring condi- 

 tions. Note the horns. 



