DECAY IN DOUGLAS EIR. 
9 
Yellow-brown top-rot, true to its name, in Table 7 shows the 
greatest number of infections entering through dead tops, which 
include broken and spike tops. Knots, though with fewer infections, 
were responsible for a greater volume of decay, since such infections 
usually occurred lower down on the bole where there was more 
heartwood for the fungus to work on than was the case when the 
wood destroyer entered through a dead top. The large volume of 
decay the cause of which is recorded as “ unknown” resulted from 
an extensive infection which could not be traced to its source. 
Table 7 .—Infection court of yellow-brown tojp-rot in Douglas fir. 
Infection court. 
Infections. 
Number, 
basis. 
Percentage of total. 
Average volume. 
Number. 
Volume. 
Board 
feet. 
Cubic 
feet. 
Board 
feet. 
Cubic 
feet. 
Knots. 
12 
26.1 
35.8 
35.7 
98 
9.6 
Fire scars.. 
2 
4.3 
8.2 
6.6 
135 
10.6 
Falling-tree scars. 
7 
15.2 
7.0 
1.9 
33 
.9 
Lightning scars. 
5 
10.9 
15.4 
15.0 
102 
9.7 
Dead tops. 
18 
39.1 
17.0 
23.8 
31 
4.3 
Unknown. 
2 
4.3 
16.7 
17.0 
275 
27.5 
Table 8 shows the infection courts of the unknown decays. Some 
of these were undoubtedly infections of the four common rots, but 
were abnormal or so small that they could not be accurately identified. 
Table 8. —Infection court of unknown rots in Douglas fir. 
Infection court. 
Infections. 
Number, 
basis. 
Percentage of total. 
Average volume. 
Number. 
Volume. 
Board 
feet. 
Cubic 
feet. 
Board 
feet. 
Cubic 
feet. 
Knots. 
5 
14.3 
0 
0 
0 
0 
Fire scars. 
12 
34.3 
80.0 
62.5 
10 
1.8 
Lightning scars. 
4 
11.4 
20.0 
8.8 
8 
.8 
Dead tops. 
11 
31.4 
0 
20.8 
0 
.6 
Roots. 
3 
8.6 
0 
7.8 
0 
.9 
In Table 9 the data in Tables 4 to 8, inclusive, have been combined. 
Knots were responsible for the greatest number of infections and a 
proportionately greater loss through decay. 
Of all the infection courts fire scars, which were only responsible 
for 4.2 per cent of the total rot volume, are the only factors that can 
be directly controlled. With the increase of efficiency in fire-protec¬ 
tion methods, injury from fires is being steadily reduced. But the 
other 95.8 per cent of the decay is traceable to sources that can not 
be controlled. Knots, falling trees, lightning, and snow or ice will 
