122 RESEARCHES ON FUNGI 



(1) The mycelium works upwards in a tree-trunk most readily by 

 way of the heart-wood, causing a characteristic decay, and out- 

 wards by way of the sap-wood, eventually reaching the cambium. 

 Apparently, the mycelium causes the death of all the living tissues 

 traversed. (2) A broad brown band is present in the wood of living 

 trees along the advance line of the invading mycelium. Within 



FIG. 43. Fomes applanatus. A large fruit-body on a Yellow Birch trunk in a wood 

 near Phillips, Wisconsin, U.S.A. Photographed by C. J. Humphrey of the 

 Forestry Branch of the United States Department of Agriculture. 



this band there is a copious production of wound-gum and an 

 excessive multiplication of tyloses. This band steadily moves 

 forward with the advancing hyphae, the tyloses and wound-gum 

 being destroyed by the mycelium along its posterior margin as 

 rapidly as they are formed along its anterior margin. The new 

 production of the tyloses resulting from the advance of the mycelium 

 shows that the invaded tissues of the host are living, while the 

 subsequent destruction of the tyloses shows that the mycelium is 

 parasitic. (3) Inoculation with the spores and mycelium of Fomes 



