DISEASES CAUSED BY WOUND FUNGI. 39 



Hum of the sulphur polyporus usually enters the trees in the crown, 

 it is hardly practicable to attempt wound treatment. The chief 

 endeaVor, therefore, must be concentrated on the removal of the 

 diseased trees. Any tree which shows signs of development of sporo- 

 phores of Polyporus sulpJiureus should be cut down at once, and all 

 of the wood affected with the mycelium of this fungus should be 

 burned. 



PIPED-ROT OF OAK AND CHESTNUT. 



r 



The disease which we distinguish under the name "piped-rot" 

 especially affects oak trees, particularly those of the black oak group. 

 (PI. V, fig. 1.) It has also been found in the beech (Fagus atro- 

 punicea (Marsh.) Sudworth) and yellow birch (Betuki lutea Michx. f.). 

 This disease has been found widely distributed throughout the decid- 

 uous forests of the Mississippi Valley. 



A similar disease, which is probably caused by the same fungus, 

 occurs in the chestnut (Castanea dentata (Marsh.) Borkh.). (PL V, 

 fig. 12.) The heartwood of affected trees has a mottled appearance, 

 showing irregular, small, pocket-like patches of white fibers, sepa- 

 rated by wood fibers still retaining almost the normal color of the 

 heartwood. The white areas first appear in the wood in the form of 

 small lens-shaped areas, which gradually increase in size longitudi- 

 nally, and after a while become confluent, so that in the course of 

 time the wood frequently shows a series of irregular white lines 

 extending longitudinally. As the disease progresses the white areas 

 change into small pockets, or holes, lined with fibers. Where these 

 holes reach any size, they frequently become filled with a dark, red- 

 brown mycelium^ In its last stages the diseased wood is composed 

 of loose masses of white fibers mixed with the brown mycelium and 

 inclosed by thin unaffected layers of wood. The preliminary stages 

 of the disease are characterized by a darker coloration of the heart- 

 wood, which starts near the center of the trunk, gradually spreading 

 outward until it reaches the sapwood. In Plate V, figure 1, this 

 darker coloration shows on the boundary between the partially 

 decayed wood and the sapwood. 



It w T ill be noted that the disease is confined strictly to the heart- 

 wood of the tree. The changes just described originate near some 

 branch stub, very much as has been described for Fomes igniarius. 

 Without referring in detail to the microscopical changes which take 

 place in the wood, it may be said that the white areas are due to a 

 lining of cellulose fibers, which stand out more or less separately 

 from one another, on the inner surfaces of the cavities. 



The piped-rot is one which, is readily distinguished from all other 

 diseases of deciduous trees on account of the speckled character of 



149 



