4 BULLETIN 799, U. S. DEPARTMENT OF AGRICULTURE. 
brown in early stages, but in its typical stage it becomes reddish 
brown, brittle and crumbly when dry, with a tendency to break 
into cubical blocks. The rot has sometimes the characteristic odor 
of turpentine. The rotted wood is carbonized by the action of the 
fungus and the cellulose is reduced. 
The rot caused by Trametes pini is characterized by the delignifi- 
cation of the wood cells attacked. White patches of unreduced 
cellulose are left. The decay produced by Poly poms schweinitzii 
seldom advances beyond the first log and is usually not more than 5 
to 6 feet up. The form of the rot column is conical from the base 
of the tree upward. 
Fomes annosus (root Fomes) on the areas studied was least im- 
portant. The sporophores of this fungus are generally found close 
under the surface attached to the roots and hidden by the forest 
mold. They are brown above, with a white spore surface and usually 
very irregular in oiitline. The early stages of decay range in color 
from lilac to reddish. In the typical stages the annual layers are sep- 
arated by the more rapid decay of the summer wood. In a radial 
section white-pitted areas with black centers may be prominent. 
Finally the wood is converted into a spongy mass. The fungus 
causes a resin flow from the base of the tree and the roots. A fine 
felty mycelium is present under the bark in the early stages of decay. 
The rot column is uniformly circular in advanced stages and may 
extend from 6 to 8 feet into the first log. 
FIELD STUDIES OF THE ROTS IN WESTERN WHITE PINE. 
Field studies of the principal rots of a particular species of tree 
which aim to develop results of practical importance must neces- 
sarily be based on data taken from a large number of felled trees. 
It was decided that 100 trees of each age class for each of the two 
types of site would be a sufficiently large number to insure the best 
results. Seven age classes were determined upon as follows: 41 to 
60, 61 to 80, 81 to 100, 101 to 120, 121 to 160, 161 to 200, and 201+ 
years. These are the age-class divisions used by the Forest Service 
in silvicultural practice in district 1. The two types of site, slope and 
bottom, were used, under each of which the seven age classes were 
ranged. Figuring 100 trees per age class and 7 age classes for each 
of the two types of site gives a total of 1,400 trees upon which 
accurate data on each tree are required in order to be fairly certain 
of the results. 
Previous to the opening of the. summer logging operations, all 
information relative to the age classes, sites, and locations of the 
various sale areas scheduled for cutting in the western white-pine 
