THE POLYPORACEAE OF WISCONSIN 17 



more often the mycelium pushes through cracks and holes in the bark 

 and forms the numerous fruit bodies so often found. 



The amount of timber injured or destroyed by this fungus has al- 

 ready been indicated above in speaking of the "ring rot" or "dry 

 rot". Very little of this fungus was found on hemlock and spruce, 

 and none was found on balsam fir. Von Schrenk finds that fir is 

 rarely attacked by it in the New England states. 



Von Schrenk has already fully described the rot produced by this 

 fungus in tamarack, spruce, and fir, and the results of my observa- 

 tions confirm his account on practically all points. 



The rot of hemlock seems to differ only slightly from that of tam- 

 arack. The wood fibers, being changed to white cellulose fibers, are 

 not so much absorbed, leaving holes or pits as in tamarack, but retain 

 their shape, size and structure in this altered condition. The change 

 to cellulose takes place on both sides of a ring of growth. The irregu- 

 lar black lines spoken of by Von Schrenk are not so numerous as in 

 the tamarack, but wherever there are cracks or holes in the wood, there 

 is a great deal of the brown incrustation which is soluble in caustic 

 potash or ammonia. 



The appearance of the rot in white pine is quite different from that 

 in hemlock and tamarack. It is known here by the names of "ring 

 rot" or "dry rot". One tree studied was between one hundred and 

 eighty and two hundred years old, and measured nearly two feet in 

 diameter. It was felled by the loggers about two days before my ob- 

 servations were made. It was found that the rot extended from the 

 ground upward about fifty-one feet through the center of the trunk, 

 making the trunk for nearly fifty feet practically worthless, except for 

 a comparatively thin shell of sapwood. The top of the tree for about 

 sixty feet was practically sound and healthy. The rot was most widely 

 spread between ten and thirty feet from the ground, and it extended 

 only slightly into two of the larger roots. At about thirty feet from 

 the ground a few small pilei were found growing from the stubs of 

 broken and much decayed branches. Other branches extending into 

 the decayed part of the trunk were not affected. 



Lumbermen regard this ring rot as one of the commonest and most 

 destructive of the enemies of the white pine. In an area of twenty- 

 five square feet there were three large white pines, averaging at least 

 two feet in diameter, that were at least as badly decayed as the one 

 described above. 



Infection in the above-described case must have taken place through 

 one of the broken branches which was about one and one-quarter 

 2 



