22 4 BULLETIN 193. 



cm. Sometimes, however, they are much smaller, from 4 to 8 

 mm., and then they are not very prominent. In such cases 

 however, the color character of the different zones and the char- 

 acter of the under surface make it possible to distinguish the 

 plant from others. 



83. Fruit bodies of Trametes abietis, shelving form. 



In this and some other forms where the zones are not very 

 distinct it is occasionally difficult to separate the species from 

 forms of Polyporus applanatus. In the latter species the tube 

 surface is sometimes yellowish. In the fresh condition, if a 

 bruise or scratch occurs on the tube surface of Polyporus applan- 

 atus the exposed parts at once change to a dark brown or black- 

 ish color. When dry, however, this test will not yield the 



