356 



Diseases of Economic Plants 



and into all branches to which it has access. Thus trees, 

 hollow with rot, may trace their downfall to infection of some 

 small branch or bark wound months or even years earlier. 

 Trees bearing the sporophores of fungi (conchs or toad- 



FiG. 185. — Stump of limb improperly removed. After 

 Ind. Agr. Exp. Sta. 



stools) are surely infected, while the absence of such evidence 

 is no sign that a tree is healthy since the infection may be 

 very old and the sporophore earlier in evidence may have 

 rotted away. 



The fungi involved in these decays are manifold. In 

 some cases one species of fungus grows upon many different 

 kinds of wood. Other fungi are more particular as to their 



