P, edulis, P. flexilis, P. lainbertiana, P. inonticola, P. palustris, 

 "P. pmderosa, P. resinosa, P. rigida, P. strobus, P. strobiformia, 

 P, *6.eda. P. virginiana, Pseudotsugataxifolia, Thuja plica ta, Tsuga 

 caa-runB.ls, T. heterophylla, and T, mertensiana. 



Polyporus schweinitzii Fr. ranks next in importance to 

 Tra^tee pJni in the natural forests. It commonly attacks the heart- 

 wood of bhe base or butts of the trunk and of the roots of coniferous 

 trees, especially the Douglas firs. The rot rarely extends farther 

 up the trunk than the first saw log. The fungus spreads frcia disea* 

 ed trees to healthy ones underground, where larger roots come in con- 

 tact with each other. miere this takes place it is comon to find 

 groups of trees affected with the fungus, and sometimes an entire 

 group of Douglas firs are killed outright. In most instances, how- 

 ever, the trees weakened by the fungus are either uprooted or broken 



off by the winds before death. 



The heart rot caused by Polyporus sctareinitzii is of a red 

 brown color, breaking into coarse cubes, and has been found in the 

 following species of treesrtties arnabolis, A. arizonica, A. balsam 

 A. conoolor, A. Orandis, A. lasiocarpa, A. shartensis, Larix laricp 

 L lyalli, 1. occidental, Picca engel^nni, Picea sitchensis, PUrw 

 aibicaulis, P. aristata, P. arisonioa, P. contorta, P. divarioata, 

 P. echinata, P. flexilis, P. la^ertiana, P. -nticola, P. murW 

 P. paiustri., P. Ponderosa, P. resinosa, P. strobus, P. 

 P. taeda, P. virginiana, P3eudot S u E a tasifolia, Tsuga m ertenBiana : 

 and T. heterophylla. 



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