DECAY IN DOUGLAS FIR, 17 
brown top-rot usually occurs in the upper bole or top. Conk-rot 
causes by far the greatest volume of decay. The other three rots 
are of relatively minor importance, except that red-brown butt-rot 
predisposes an infected tree to windfall. 
Douglas fir is subject to wounding throughout its life and partic- 
ularly to injury by fire during its earlier years. On the whole, wounds 
in Douglas fir are mostly superficial, and this tree species heals 
rapidly after wounding. Scars callus very irregularly, and it is 
usually difficult or impossible to determine the exact dates when 
scars were made. 
Mechanical injuries are of little importance in relation to the 
entrance of decay. Knots were responsible for nearly 90 per cent of 
the volume of all decay in the trees studied, lire scars were the 
entrance point for 4 per cent, and the remaining 6 per cent came in 
through other scars, r ire is the only factor which is controllable, so 
there can be but little reduction in the extent of decay in future 
stands by a reduction in the scars caused by controllable mechanical 
injuries. 
Recognition of the indications of decay in standing or felled timber 
is of the greatest importance from a practical standpoint, yet this is 
little understood. Branch fans, dead limbs, or burls do not indicate 
decay. Sporophores and swollen knots which develop prolifically 
indicate the presence of conk-rot. After a stand has been fire swept, 
burned-out hollows show where there were sporophores and swollen 
knots. It is also possible to approximate with some accuracy the 
volume of the decay. Conk-rot, on the average, extended approxi- 
mately 20 feet in the trunk beyond the highest or lowest sporophore 
and 10 feet beyond the highest or lowest swollen knot. Sporophores 
of red-brown butt-rot are not common. However, the relative fre- 
quency of fire scars indicates somewhat the relative amount of this 
decay. Churn butts often denote old fire scars. Brown trunk-rot 
is rather difficult to detect in standing trees, but the loss caused by 
this decay is insignificant. This also applies to yellow-brown top-rot. 
Figures on the different rots, giving the extent of incipient decay 
beyond typical decay, show that this is rather variable, thus requir- 
ing careful inspection to obviate the inclusion of wood with this type 
of defect in timbers selected for durability and strength. 
OUTLOOK. 
The work on which the preceding discussion is based is merely pre- 
liminary. More extensive studies are needed to bring out new facts 
and develop still further those already brought out. This should 
aid materially in placing the estimating of Douglas-fir timber on a 
more exact basis. 
The biggest problems remain unsolved. Our half -formula tod ideas 
of control of decay in Douglas fir are based on obsen at ion without 
a sound backing of exact data. Furthermore, while it is a well- 
established fact that young stands or second growth arc relatively 
immune from decay, it is not yet determined at w hat age in the life 
of the stand this immunity ceases and the trees become subject to 
csivc decay. Establishing this age will enable us in the future 
