DECAY IN DOUGLAS FIR. 7 
Lightning wounds occasionally occurred, although the Douglas fir 
region is not subject to severe lightning storms. Injury by sap- 
suckers was rare, and the few scars found were very superficial. 
These birds do not seem to select a single tree and attack it year 
after year, as they often do in other tree species. Frost cracks were 
not common. This was to be expected, since the Douglas fir r<\ 
as a whole is not subject to sudden extreme variations of temper- 
ature from relatively warm to very cold. 
There were 10 spike-topped trees. Half of these dead tops had 
been caused by lightning, while two of them resulted from falling 1 1 
On the other hand, trees with broken tops were not unusual. The 
most common cause of such injury was falling trees. This source 
accounted for 31 of the broken tops. Snow was responsible for 4 and 
lightning for 3, while the remaining 20 could not be determined. 
A load of ice or heavy wet snow is of more importance in causing 
broken tops than appears from these figures, but most of the damage 
occurs in young stands. According to observations of the writer and 
others, heavy snow or ice injury occurred about 1888 3 in the imme- 
diate section where this study was made. The damage was very 
apparent from the number of broken tops, all having been made at 
the same time, in second-growth timber. 
Broken tops require a long time to heal. Even after the volunteer 
top is well started the stub of the old top protrudes, and when this 
is finally grown over a slight crook still remains in the bole, which 
does not entirely disappear for years. 
In considering the data presented, it may appear from the total of 
508 scars on 158 trees that the trees were subject to excessive injury. 
It must be remembered that most of the wounds were superficial. 
Then, too, several small scars on a single tree might be made by the 
same agent. For example, one fire or one lightning stroke can 
readily cause several scars on a tree. Owing to the impossibility of 
determining with any accuracy the dates of injury in Douglas fir, it 
was necessary to consider each scar, with a few exceptions, as separate 
and distinct. 
ENTRANCE OF THE DECAYS. 
The wind-blown spores from sporophores of wood-destroying fungi 
attacking the heartwood of living trees must light on exposed dead 
wood in order to cause infection. But the type of infection court 
varies with different species of decay, and it is of importance to 
determine the common means of entrance in each case, since in so 
far as the infections occur through controllable mechanical injuries 
there is a possibility of reducing the amount of loss. 
Table 4 shows the points of entrance for conk -rot. From this 
table it can be seen that knots or branch stubs are responsible for 
the major portion of the infections, and, what is far more important . 
all but an infinitesimal portion of the total volume of conk-rot 
resulted from these infections. 
The infections of brown trunk-rot both numerically and in the 
resulting volume of decay were rather more evenly distributed, as 
can be seen from Table 5; but here again knots predominate. 
'This date is from an unpublished record furni ice. 
