INJURIOUS INSECTS, FUNGOUS DISEASES, ETC. 191 



The effect of the destruction of the heart-wood of trees 

 brought about by this fungus is of a nature resembling the 

 decay caused by the false-tinder fungus ; and what has been 

 said regarding methods of control of the latter applies to 

 this species as well. 



Heart-Rot of Sugar Maple {Hydnum septentrionale Fr. ) . 

 This fungus is found principally on the sugar maple ; but 

 also on other species of deciduous trees. The effects of this 

 fungus upon the wood of diseased trees produces a heart 

 decay similar to that of the false-tinder fungus. 



The color of the sporophores is creamy white, and they 

 appear in bracketlike clusters that have a striking appear- 

 ance. 



SAP-ROTS OF TREES 



In the economy of nature many fungi serve a useful 

 purpose in breaking down dead wood and clearing the 

 forest of debris. Fungi which grow only on dead wood are 

 saprophytic, while those which feed on living tissue are 

 parasitic. Frequently no sharp line can be drawn between 

 those fungi which are capable of growing on dead wood that 

 has died after being cut from a living tree and the fungi 

 which grow on dead wood of the still living tree. Some of 

 these fungi are mentioned in this connection because they 

 are frequently taken to be the cause of disease. 



The Common Bracket Fungus {Elfvingia megaloma 

 (Lev.) Murrill) (Fomes applanatus (Pers.) Wallr.) may be 

 taken as a type of this class of fungi. It is frequently found 

 on living trees, but a careful examination always shows it to 

 be growing on wood which is actually dead. Generally this 

 is the outer sapwood. The sporophores or fruiting bodies 

 of this fungus constitute brackets. The upper surface is 

 more or less marked by concentric zones which divide off 



