216 ^MANUAL OF TREE DISEASES 



of the causal fungus are formed abundantly on the diseased 

 trees and on fallen logs. They have a red varnished margin 

 and a cream-colored under surface. Fuller details concerning 

 this heartwood-rot will be foimd under fir diseases, page 165. 



Bkoatn Heaktwood-Rot 



Caused by Forties officinalis Fries ( = Fames laricis (Jacq.) Murrill) 



This brown heartwood-rot is common and very destructive 

 in western United States in larch, pine, Douglas fir and other 

 conifers. In California and Nevada, sugar pines are the most 

 destructively attacked. In the Northwest, Douglas fir, western 

 larch, lodge-pole and western yellow pine are often seriously 

 affected. The rot resembles to some extent the brown checked 

 wood-rot caused by Polyporus svlphurnis (see page 247). 



Symptoms. 



The affected heartwood is brownish or red-brown in color. 

 Felts of the mycelium of the fimgus form in cracks in the wood. 

 The sporophores of the causal fungus are not formed abun- 

 dantly on the affected trees. They are large hoof-shaped or 

 globose bodies with a white, roughened, chalky upper surface. 

 The white material will rub off like powdered chalk. The 

 fruiting-bodies when young are soft and waterj- but become 

 very brittle when old. The inner structure is white,* bitter to 

 the taste and has a distinct mealy odor. The under surface is 

 convex, whitish and covered with small pores. 



Caiise. 



The brown heartwood-rot of conifers in the western forests 

 is caused by Fames officinalis. This fungus also is known by 

 the name Fames laricis. Infection takes place when the spores 

 from the tubes on the under side of the fruiting-body lodge in 

 open wounds where heartwood is exposed. For further detail 



