THE POLYPORACEAE OF WISCONSIN. 21 



tree was felled and sections were cut out. Rot like the above de- 

 scribed was found extending from the base to about eight feet upward. 

 At a height of about seven feet only a few "strands" of decay were 

 found between the heartwood and the sapwood on the side of the tree 

 which was wounded. The center and the rest of the tree here 

 were sound and normal. Four feet above ground the rot had 

 extended over half way around the center, which was still quite sound 

 here, but in the sapwood it reached the surface, where little knots of 

 white mycelium indicated the beginning of pilei. About one foot 

 above the ground the entire heartwood and most of the sapwood, ex- 

 cept that on the side opposite the wound, were reduced to the brittle 

 brown condition. On the side opposite the wound, the tree was sup- 

 ported by a shell of sound living sapwood, about one inch in thickness 

 and nine inches in width. Numerous small pilei were growing out of 

 the wound at this height. The roots were sound also, except one or 

 two of the largest ones into which the rot extended for several inches. 



The top of the tree was green but had a sickly appearance. Some 

 of the lower branches were dead and others were losing their needles. 

 The growth of the year of the twigs and tips was less than that on 

 other trees near by, as though the tree was lacking in strength and 

 nourishment. It was plain that even if the tree escaped the storms, 

 it would be dead in a few years. From the evidence in this ease we 

 may conclude that: 



First: — Infection may take place in wounds, and the decay is 

 greatest in the region of infection, if the wounds are near the base. 

 This was shown by the fact that near the base where the wound was 

 largest, there was the most rot. At that point the mycelium first pene- 

 trated and hence had had a longer time to produce its effect. Here 

 also were most of the pilei. 



Second: — The spread is upward, radially and tangentially, and 

 downward. The spread directly upward is very much more rapid 

 than in any other direction, and downward it is least rapid. The 

 spread is more rapid tangentially than radially, following the rings 

 of growth. It spreads to the center only when most of the rings in 

 which it is found are used up. This is evident from the section at a 

 place four feet above the ground, where the sound center was nearly 

 surrounded. 



Third: — The decay spreads only very slowly into the roots of the* 

 tree. 



Fourth: — The spread and reduction of wood is quite rapid, as all 

 of this rotting must have been completed within a period of twelve 

 years. 



