25 



the trunks and branches above ground. Old knot holes or branch 

 wounds, wounds produced by fire, or wounds made by animals, are 

 favorable spots for the entrance of the spores. Wherever a tree 

 dies from any cause this fungus is sure to attack it before long. In 

 the sections where the bark beetles had been active some years ago 

 there were many trees the wood of which had been destroyed by this 

 Polyporus. 



The large holes made by woodpeckers offer excellent opportunities 

 for the entrance of spores. As the woodpeckers are very active in 

 exterminating insects inha])iting the bark (presumably the bark beetles 

 among others), we have here a case of their allowing one enemy to 

 enter while destroying another. In old windfalls the dead trees were 

 covered with sporophores, some of them many years old, showing that 

 these trees had become infected very soon after the trees had been 

 blown over. This fact is of importance, as it suggests that these trees 

 could be saved by the lumberman if carried to the mills shortly after 

 their downfall. This will be referred to again. Plate IV is from a 

 photograph of a portion of a Spruce trunk. The small white spots in 

 the bark are holes of a borer filled with the mycelium of the fungus. 



STRUCTURE OF DISEASED WOOD. 



Wood of the Spruce in which the m^'celium of this Polyporus has 

 been growing for some time deserves the description "entirely rotted" 

 par excellence. The wood has been changed to a 1)rittle red-brown 

 mass, which has cracked in many directions. The individual pieces 

 are barely held together by countless sheets of mycelium which have 

 filled the spaces resulting from the cracking of the wood and form an 

 intricate network of larger and smaller sheets. In PI. IV a portion 

 of a log in the last stages of decay is shown. At one side a sporo- 

 phorc one year old and another just beginning are visible. The sap- 

 wood has mimerous tunnels of a borer filled with remnants of the 

 borings. Such wood has lost all strength, and falls to pieces at the 

 slightest touch. If the mycelium attacks a standing tree the decay 

 goes on within it until the trunk becomes so weak that an ordinary 

 wind blows it over. The shrinkage which takes place in the wood as 

 it is being metamorphosed is very considerable, as is evidenced by 

 the large number of wide cracks which fill it, passing both across the 

 annual rings and parallel to them. 



The changes which result in the wood may be descril)ed as follows: 

 In a tnra just attacked the wood a))out the point of entrance of the fun- 

 gus turns darker jind finally becomes a decided red-bi'own. Before k)ng 

 small whitish areas appear here and there scatt(n-ed irregularly through 

 the wood. Some of these are mere lines, while others form white 

 patches circular in shape, surrounding small areas of wood about the 

 size of a pinhcMid, which are red-brown (PI. III). Others again have 



