PRINCIPAL GROUPS OF PLANTS 



55 



color which are pustules of the fruiting fungus. These pustules 

 produce mostly winter spores (ascospores), although occasionally 

 a long strip of summer spores (conidia) are also produced (Figs. 

 31 and 32). 



FIG. 31. Typical appearance of branches of Chestnut tree affected with chestnut 

 blight. At left, bark showing pustules of the parasitic fungus bearing winter spores. At 

 right, the diseased bark showing pustules and form of discharge of summer spores in damp 

 weather. From photograph by Haven Metcalf. 



The control of the disease over large districts consists mainly 

 in destroying the affected trees and carefully burning the rubbish. 



