DISEASES CAUSED BV WOUND FUNGI. 25 



biiim, and where they are allowed to develop to any extent their 

 destructive action may extend completely around a tree, resulting 

 in the death of branches, and sometimes of the entire trunk. The 

 slime-flux diseases can hardly be considered of great practical impor- 

 tance and only become so where valuable shade or park trees are 

 affected. As a preventive measure, the precautions to be taken for 

 wounds, referred to farther on. are applicable. 



DISEASES CAUSED BY WOUND FUNGI. 

 WHITE HEART-ROT CAUSED BY FOMES IGXIARIUS. 



The principal diseases of deciduous forest trees are caused by a 

 group of fungi which grow in the heartwood of the trees. The chief 

 interest which attaches to the maintenance of wood lots or forest 

 tracts comes from the fact that such tracts are maintained for the 

 wood which they produce. Anything, therefore, which either reduces 

 the rate of wood production or actually destroys the wood formed is 

 of particular interest. 



The fungi which are responsible for the decay and destruction of 

 the heartwood of various broadleaf trees are quite numerous. 

 They are more or less alike, however, as to their manner of entrance 

 into the tree, their subsequent development, the production of their 

 fruiting bodies, and the manner of prevention. In the following, 

 one of the commonest of these fungi, the so-called "false-tinder 

 fungus" ( Fomes igniarius (L.) Gillet), is taken as a type, and such 

 specific differences as apply to the other forms are given in the special 

 chapters in the latter part of this bulletin which are devoted to the 

 more important of these wood-rotting fungi. 



XATURE OF DISEASE CAUSED BY FOMES IGXIARIUS. 



The disease of deciduous trees caused by the false-tinder fungus 

 ( Fomes igniarius) may be called the "white heart-rot." It is usually 

 confined to the heartwood of the tree, including the trunk and larger 

 branches, but it may also affect the sapwood. As a result of the 

 action of the false-tinder fungus the heartwood is changed into a 

 whitish, soft substance, which differs little in the different species of 

 hosts. 



A tree attacked by the fungus shows no particular change in its 

 general external appearance during the early stages of the disease: 

 in fact, it is practically impossible to recognize a diseased tree until 

 the fruiting bodies of the fungus form on the outside of the trunk. 

 During the later stages of the disease affected trees can be recognized 

 by the presence of the fruiting bodies of the fungus, of which there 

 may be from one to a dozen on a single tree, at or near wounds, branch 



