524 



SPECIAL PLANT PATHOLOGY 



leaves are expanded fully. The epidermis is pushed up by short conidio- 

 phores which arise from a hyphal stroma beneath. These conidio- 

 phores produce unicellular, curved conidiospores which serve to dis- 

 tribute the fungus. Formerly this stage was called Melosmia. Later 



r-^ 



Fig. 1 88. — Cross-section of branch of dead beech rotted by Fomcs fomenlarius. 

 (After von Schrenk, Hermann, Bull. 149, U. S. Bureau of Plant Industry, pi. viii, 

 1909.) 



as the season advances, the hyphae become massed into a sclerotium- 

 like area black without, but white within, and this persists after the fall 

 of the leaf. Sometime the next spring, there arise from these sclerotia 

 complex apothecia often 1.5 cm. broad, which break through at irregular 



