WESTERN RED-ROT IN PINUS PONDEROSA. 3 



From these radial patches the rot spreads in all directions, until 

 finally the entire heartwood is involved. In tangential sections 

 these radial patches of rot appear as irregular elliptical reddish to 

 brown areas with white centers. These areas are two to several 

 times longer than broad, with their greatest diameter lying parallel 

 with the grain of the wood. There is often a small cavity bordered 

 by the unabsorbed remnants of the delignified tissue in the center of 

 each rotted area. Usually two to six of these discolored areas are 

 grouped together, giving the sawed lumber a very peculiar appear- 

 ance. 



COMPARISON OF WESTERN RED-ROT AND TRUE RED-ROT. 



When examining the rot in the end of a freshly cut pine log it 

 is often difficult to determine whether it is western red-rot or true 

 red-rot. A longitudinal view of the rot, however, usually will settle 

 the question beyond any reasonable doubt, since the following con- 

 stant characters are then in evidence: (1) True red-rot, or red-heart, 

 caused by Trametes pini, has many small but sharply defined pockets, 

 or cavities, in the heartwood, lying parallel to the grain of the wood, 

 while western red-rot never has these typical pockets. (2) The 

 attacked wood in true red-rot is usually very firm, even in the final 

 stage of the rot, while western red-rot in its last stage is much dis- 

 integrated and easily crumbles when handled. (3) The mycelium 

 of true red-rot when growing in heartwood which is more or less 

 exposed to the air is brown, while the mycelium of the western red- 

 rot is always white. (4) The attacked heartwood in true red-rot 

 never becomes wet and soggy, as it often does in certain stages of 

 western red-rot. 



CAUSE OF WESTERN RED-ROT. 



The fungus which causes western red-rot never forms brown, 

 woody, perennial fruiting bodies on the boles of living affected pine 

 trees, as Trametes pini does, but forms annual fruiting bodies, which 

 are usually developed as white encrusting layers on the under side 

 of logs lying on the ground. This fungus is also the main agent in 

 rotting the sapwood of the cull logs and large branches of the yellow- 

 pine slash. 1 



The fruiting bodies, or sporophores, of this fungus, as they occur 

 in Arizona and New Mexico, are usually resupinate, with a hymenial 

 layer consisting of minute tubes or pores. However, fruiting bodies 

 have been found which have distinct and well-formed piiei. The 

 pileate form of the fungus resembles very closely Polyporus eUiskinus 

 (Tyromyces ellisianus of Murrill in North American Flora) : the 



1 Long, W. H. A new aspect of brush disposal in Arizona and Xew Mexico. In Proc. 

 Soc. Anier. Foresters, v. 10, no. 4, p. 383-398. 1915. 



