236 MANUAL OF TREE DISEASES 



rays are destroyed and the porous portion of the annual rings 

 is delignified and partially dissolved. The denser summer- 

 wood of the rings is least affected. The result of this action 

 is that the affected wood is light in weight and breaks easily 

 into flakes. 



The sporophores of the causal fungus are fleshy, annual, 

 shelving structures with radiating plates or gills on the under 

 surface. The sporophores are more or less sessile and appear 

 in clusters at wounds where the affected wood is exposed. 

 They are often found at the junction between two limbs. The 

 upper surface is smooth, slightly rounding and white or gray- 

 ish in color. The gills on the under surface extend on to the 

 stalk-like attachment to the wood. For more complete detaUs 

 concerning the life history and control of the wood-rotting 

 fungi, see page 64. 



Reference 



Leam, C. D. Studies on Pleurotus ostreatus Jacqu. and Pleurotus 

 iilmarius Bui. Annales Myeol. 10 : 542-^556, pis. 16-18. 1912. 



White Butt-Rot 



Caused by Fames applanatits Fries 



The heartwood of the lower part of the trunk and roots of 

 maple is sometimes destroyed by this rot. The decayed 

 wood is whitish, light in weight and has many white-stuffed 

 tunnels running in the horizontal direction. The sporophores 

 of the causal fungus are shelf-like, woody bodies, with a smooth 

 brownish upper surface and a white under surface. Further 

 details concerning this heartwood-rot will be found under 

 poplar diseases, on page 310. 



