22 THE POLYPORACEAE OF WISCONSIN. 



Fifth:— Quite a little mycelium must form before piloi are produced, 

 as none of the pilei were more than three years old. 



Other similar examples were found but none so striking as the one 

 described. The place of entrance in the pines and fir trees is not al- 

 ways easy to determine. One small fir was cut down and examined. 

 It was forty-five years old and three inches in diameter. In the 

 jstump, one inch under the ground, was a wound about an inch in di- 

 ameter. From this place the rot extended upward into the trunk 

 aDout three and one-half feet, through the center and a few inches 

 into four of the larger roots. No pilei had as yet been formed, as the 

 rot had not reached the surface at any place except near tho Wound, 

 and that was under ground. However, the rot was unmistakably that 

 of F. ungulatus. In several red and white pines the small pilei were 

 growing through holes in the bark, and it is possible that infection 

 took place here. 



The carbonization of the wood by this fungus is quite complete. In 

 the advanced stage it does not burn with a flame but smoulders like 

 charcoal, giving off a comparatively small amount of smoke. 



The transition from decay to healthy wood is remarkably abrupt, 

 there being apparently no intermediate stage between the decayed and 

 the sound wood. One ring of gi'owth may be healthy and vigorous, 

 and the next one to it may be entirely broken down. 



In small areas here and there, traces of cellulose may be found. In 

 these spots the secondary lamellae do not have'the spiral cracks found 

 in the other parts. In most of this tissue no cellulose reaction can be 

 found. It all stains bright red with phloroglucin, even when in the 

 last stages of decay. The secondary lamellae crack spirally, and 

 finally the middle lamella also becomes brittle, so that the whole wood 

 structure can be easily rubbed into a fine powder with the fingers. In 

 many cells there are numerous holes through which hyphae pass. 

 There seems to be little absorption of the wood after change, and no 

 cavities appear as in the ring rot. However, the meduUary cells show 

 some absorption. This may account for the radial cracks in which 

 the mycelium grows, as suggested by Von Schrenk. 



