MAPLE DISEASES 235 



are three or four inches long and project two or three inches 

 from the tree. The under surface of the shelves is composed 

 of pendent bristles or teeth (Fig. 43). The spores are borne 



FiQ. 43. — Lengthwise section through a f ruiting-body of 

 Hydnum septentrionale. 



over the surface of the teeth. The life history and control of 

 the wood-rotting fungi are more fully discussed on page 64. 



White Streaked Sapwood-Rot 



Caused by Pleurotus ostreatus Jacqu. 



Maples and other deciduous trees, such as basswood, elm 

 and oak, are sometimes found affected by this sap wood-rot. 

 Infection takes place in open wounds caused by various agents. 

 The decayed area of wood is lighter in color than the normal 

 wood and is bounded by a narrow brown zone. The medullary- 



