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. 



FIG. 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 Volutellafructi. 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 



