ARMILLARIA 



355 



root is first attacked, the mycelium gradually passing into the 

 collar and lower portion of the trunk. The injury does not 

 penetrate very deeply into the wood, but as the cambium 

 and outer layers of sap-wood are gradually killed, the tree 

 eventually dies. If the bark is removed from the collar or 





3 



FIG. 108. Armillaria mellea. Group of plants about 

 one quarter nat. size. 



lower part of a tree that has been killed by the fungus, a 

 sheet of pure white mycelium is seen investing the wood. 

 The same appearance is observed in the root. In the case 

 of conifers a considerable accumulation of resin is present at 

 the collar ; for this reason the disease was at one time known 

 as resin-flux. The white mycelium between the wood and the 

 bark often presents a fasciated or fan-like appearance and breaks 

 up into strands, which either continue to extend between the 



