218 



BULLETIN 193. 



trunks of the beech bearing the Polyporus igniarius collected^at 

 Childwood, N.Y., in 1896, presented the same characteristic col- 

 oration and marking. The maple is said by some lumberman to 

 be troubled by a disease which they term " black heart." It 

 would be interesting to know if the coloration produced in the 

 heart by the action of the mycelium of Polyporus igniarius is 

 identical with this "black heart " disease. 



It now becomes a matter of interest to determine the mode of 

 entrance of the mycelium of this fungus into the tree. The 

 fruit bodies were found to be situated at wounds. These 

 wounds, or places of exit for the fruit form of the fungus, were 

 " knot " holes formed by the dying away of the lower limbs, and 

 the failure of the healing tissue to close the wound thus formed. 

 The fruit form can make its exit through quite a small opening, 



77. Effect of mycelium of Polyporus igniarius on 

 wood of beech. 



and usually does, growing to larger dimensions outside as it 

 ages. The first year's growth of the fruit form may then be 

 quite small, as in Fig. 79 where it is but a small protuberance i 

 to 2 cm. in diameter and showing no fruiting surface. This 

 often increases in size each year, slowly, until 4 to 5 cm. in 

 diameter, when it may increase more rapidly and each year form 

 a new fruiting surface beneath. 



The young fruit form shown in the photograph is on a trunk 

 of a maple 10 cm. in diameter. This was the only evidence 

 that the tree was diseased, all the other wounds at fallen limbs 



