22 BULLETIN 871, U. S. DEPARTMENT OF AGRICULTURE. 



any definite information, but certainly the chemical and physical 

 condition of the substratum must have a strong bearing on this 

 phenomenon. Hartig (9, pp. 115-116) believes in the case of Poly- 

 porus (Fomes) igniarius that the width of the annual rings of the 

 wood is not without influence on the rapidity of decay. Munch (20, 

 p. 156) states that the more rapidly grown coniferous wood, conse- 

 quently that with the broader annual rings, is more speedily decayed 

 by Fomes annosus than slower grown wood with narrower rings, even 

 extending this to broad and narrow rings in the same individual. 

 Later (22, p. 403-406), he shows that suppressed individuals of beech 

 artificially infected with Stereum purpureum. 8. rugosum, Polyporus 

 (Fomes) igniarius, and P. (F.) fomentarius were more seriously de- 

 cayed than dominant thrifty trees, yet it is just such suppressed trees 

 which must have the narrowest annual rings. Finally (23, p. 521), 

 the same investigator finds no relation whatsoever between the 

 breadth of the annual rings and the rapidity of decay in the wood of 

 oak attacked by Polyporus (Fomes) igniarius. 



PURPLE COLORATION. 



Accompanying the dry-rot is a purplish coloration of the heartwood 

 which is very characteristic. The writer does not find this mentioned 

 in any description of the dry-rot so far available, but it is well known 

 to the lumberman. This color varies from a light salmon-red or pink 

 to a pronounced purplish red in trees with heavy decay, where it may 

 stand out strongly in cross section as a ring surrounding the decayed 

 area or present a mottled appearance over the entire heartwood. 

 Where the coloration is faint it is sometimes impossible to detect it 

 in cross section, but if the tree is split longitudinally the color is 

 readily apparent, although it often fades out entirely after several 

 days' exposure to light and air. It usually commences at ground 

 level and extends upward, but may start at varying heights. 



Microscopical studies of this colored wood did not show any devia- 

 tion from sound wood. No hyphse were found except at points im- 

 mediately adjacent to pockets of dry-rot. No chemical or physical 

 examination was possible. 



In all, 634 trees were dissected in which the purple coloration was 

 present. The notes from Cow Creek did not include data on this 

 coloration. The youngest tree in which the coloration was present 

 had an age of 72 years, while the youngest tree cut was 52 years old. 

 No attempt can be made to set a minimum age limit for trees with 

 purple coloration, since not many trees were cut below the age of 

 70 years. 



Of the 634 trees under consideration, the purple was present in 84 

 in which no dry-rot was found. In these the coloration, varying 

 through all shades from a very faint salmon pink to pronounced red- 



