OAK DISEASES 255 



or entirely hollow trees are thus formed. The cavities are 

 filled or lined with yellowish mycelium. 



The fruiting-bodies of the causal fungus are formed annually 

 at wounds or insect tunnels. They are globose and may be as 

 large as a foot across. The upper surface is hairy and covered 

 with drops of water. The under surface and the margin of the 

 fleshy fruiting-body are covered with numerous long pendent 

 spines or teeth. Insects soon destroy the fruiting-body. 



Qause. 



The wet heartwood-rot of oaks and other trees is caused by 

 Hydnum erinaceus. The spores are borne over the outer sur- 

 face of the teeth on the under side of the fruiting-body. They 

 are disseminated by the wind and infection takes place in 

 wounds of all sorts. Further details concerning the life history 

 and control of wood-rots will be found on page 64. 



Reference 



Schrenk, Hermann von, and Spaulding, P. Disease caused by Hydnum 

 erinaceus. In Diseases of deciduous forest trees. U. S. Dept. 

 Agr. Bur. PI. Ind. Bui. 149 : 44-45, pi. 7. 1909. 



Honeycomb Heartwood-Rot 



Caused by Stereum suhpileaium Berkeley and Curtis 



This heartwood-rot of oak is common in Arkansas, Missis- 

 sippi and Louisiana. It is also found in Kentucky, Ohio, 

 Missouri, Virginia and Florida and probably is generally dis- 

 tributed over southern United States. Several species of oaks 

 are affected. The sapwood is not destroyed and the sporophores 

 of the fungus occur only on dead fallen trees or on dead areas 

 in living trees. 



Symptoms. 



The affected wood is at first slightly discolored and water- 

 soaked. Light colored areas appear at various places in the 



