4 BULLETIN 199, U. S. DEPARTMElsTT OF AGEICULTUEE. 



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 clecaj^ produced by Polyporus schweinitzii 

 seldom advances bej^oncl 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 outline. 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 



