APPLE DISEASES 133 
with fruiting pustules (Fig. 35, left); these are largest in the 
central region of the spot and are evident within a quarter of an 
inch of the margin. If examined with a hand-lens, stiff dark- 
brown hairs may be observed protruding from the fruiting bodies. 
Fic. 35. — Spongy dry-rot; various stages of development. 
These constitute an important diagnostic sign of the disease. 
The affected tissue is spongy and dry, whence the name spongy 
dry-rot. 
Cause. 
This apple-rot is caused by the fungus V olutella fructi. With- 
in the fruiting bodies mentioned above conidia are produced._, 
These germinate in a manner similar to the process exhibited= 
by the spores of other fungi. The germtubes enter the apple- 
fruit through injuries of various kinds. Within the flesh 
mycelium develops profusely and after a few days the rot is 
evident. Before a lesion has attained a very great diameter 
the fruiting bodies appear. Mycelium develops abundantly 
beneath the cuticle and soon a mycelial cushion is formed. This 
continues its growth until the skin is ruptured and the structure 
