DECAYS AND DISCOLORATIONS IN AIRPLANE WOODS. 35 
ance of cellulose pits. Hence, the purplish red color commonly found 
in the heartwood of incense cedar (see p. 16) and western red cedar 
need not be mistaken for decay. 
As yet very little is known in regard to the reduction in strength 
due to incipient decay caused by the ring-scale fungus. However, it 
seems probable that such reduction is slight until the appearance ‘of 
the white cellulose pits; but it is to be remembered that pieces with 
discoloration contain hy phe which may again attack the wood, if 
suitable conditions arise. Consequently, stock with any stage of this 
decay should not be used. 
The chalky quinine fungus causes a pronounced decay in the heart- 
wood of many softwoods. The typical decay is a brownish red 
friable crumbly mass, often with conspicuous mycelium felts filling 
the cracks. This is shown in Plate IV. The incipient decay is very 
difficult to detect, as a rule. Even when the wood has been severely 
weakened the extremely faint brownish discoloration is not discern- 
ible to any but the most expert eye. However, the incipient stage 
of this decay in western yellow pine appears as a red-brown or pro- 
nounced brown discoloration in the pale-lemon to light. orange- 
brown heartwood. ‘The discoloration is not uniform over the entire 
affected portion, but may occur on the radial or tangential face in 
broad bands of varying intensity or even intermingled with narrow 
bands of the normal light-colored heartwood. In cross section the 
infected wood presents a mottled appearance. The horizontal limits 
of the discoloration are bounded by a narrow band of pronounced 
pink or red. At the upper limits of the incipient decay the discolora- 
tion becomes fainter until it finally disappears. The discolored wood 
seems to be hard, firm, and strong, but in reality it is seriously weak- 
ened. Plate V illustrates this condition. 
The typical decay caused by the sulphur fungus (Polyporus sul- 
fureus (Bul.) Fr.) is very similar to the foregoing. However, it is 
not confined to softwoods. It is common only in the true firs among 
the softwoods, but is very prevalent among the hardwoods, particu- 
larly the oaks. The heartwood of living and dead trees is affected. 
The incipient decay is difficult to detect, being first indicated by a 
faint brownish discoloration. 
The velvet-top fungus (Polyporus schweinitzii Fr.) also causes a 
reddish brown friable rot, which is, however, confined to the butt and 
roots of the tree. The mycelium felts are very fine and inconspicuous. 
Only softwoods are affected. Normally the incipient decay is very 
difficult to detect. It first becomes evident i in Sitka spruce ® as pale- 
yellow to lemon-yellow streaks or spires extending longitudinally 
beyond the light yellowish to reddish brown discoloration which 
characterizes the more visible incipient decay. In the latter stage a 
softening of the wood is apparent. In Douglas fir the incipient decay 
is first evident as a faint yellowing or browning of the normal heart- 
wood. This or an exactly similar. decay in western red cedar is first 
indicated by a decided deepening in the color of the normal brownish 
heartwood. The discolored zone often extends horizontally for sev- 
eral inches around the typical decay and for a foot or more in ad- 
vance of it. The discoloration may be confused with the normal 
©The description of the decay in this species caused by poLpare schweinitzii is based 
on notes furnished to the writer through the courtesy of E. E. Hubert. 
