136 MANUAL OF TREE DISEASES 



trunk being most often decayed. Trees less than one or two 

 feet in diameter are not usually attacked. 



Symptoms. 



The appearance of the affected wood is very similar to the 

 pecky heartwood-rot of cypress (see page 97). Long lens- 

 shaped pockets are formed parallel with the grain of the wood. 

 The pockets are filled with a brittle brown mass of decayed 

 wood. The surface of the pockets is smooth and the wood 

 immediately siurounding is sound. The first evidence of 

 the decay is the darkened color of certain areas varying from 

 one to ten inches long and from one-fourth to one inch wide. 

 The affected wood in these areas is quickly reduced to a brown 

 diarcoal-like mass. The pockets vary in arrangement and 

 number much as in the pecky heartwood-rot of cypress, and 

 a similar brown humus-like powder is found in the cells around 

 the margin. The sporophores of the causal fungus are hoof- or 

 bellrshaped bodies appearing at knot-holes in affected trees. 

 They are large bodies, several inches across, soft and spongy 

 when young and later becoming tough and chalky. The upper 

 surface is at first light brown in color but soon becomes darker 

 brown, especially around the margin. The under surface is 

 yellow or yellow-green and tm-ns brown with age. The pores 

 are small. The fruiting-bodies are soon destroyed by insects. 



Cause. 



The pecky heartwood-rot of incense cedar has been shown 

 to be associated with the fruiting-bodies of the polypore, named 

 Polyporus amarus. This fungus was previously called Poly- 

 poms Libocedrus von Schrenk. The spores borne in the tubes 

 on the under surface of the fruiting-body cause infection of the 

 heartwood of the cedar at branch wounds. The sapwood is 

 not affected. For the details of the general life history and 

 control of wood-rots, see page 64. 



