DRY-ROT OF INCENSE CEDAR. 
47 
This is because of the avoidance by the fungus mycelium of the wood 
around open fire scars. 
Infections through broken or dead tops may be absolutely disre- 
garded, both numerically and in respect to the resulting decay. 
Out of the 75 trees with these injuries only one infection occurred, 
and this resulted in a negligible amoimt of decay. 
However, the true relation of these various types of mechanical 
injuries to one another in respect to their importance as a means for 
the entrance and development of dry-rot on the areas studied is not 
expressed by the percentage of the total infections for which each 
type of injury is responsible, but must be shown by the relation of 
the number of trees infected through each type of wound to the 
total number of trees both sound and infected. The figures in 
Table XI express this relation, which might be termed " percentage 
of risk of infection." In one set of figures is expressed, then, for the 
trees actually studied the numerical relation of the various types of 
injuries combined with the relative chances for inoculation offered 
by each. All the areas are combined. 
Table XI. — Risk of infection of incense-cedar trees with dry-rot entering through wounds 
of the various types. 
Cause of wounding. 
Risk of 
infection 
(per 
cent). 
Cause of wounding. 
Risk of 
infection 
(per 
cent). 
Fire 
40.0 
15.8 
1.6 
1.2 
Frost 
.5 
.1 
The figure 40 for fire expresses the fact that of all the trees analyzed 
each tree had 40 chances out of 100 of being wounded by fire and 
subsequently becoming infected with dry-rot through this wound, 
and so on for the other types of injury. 
The far greater importance of fire wounds as a means of entrance 
for dry-rot as compared with all other injuries is strikingly brought 
out. Knots, the nearest competitor, are far less important, while 
all the others practically can be neglected. 
The close relation of wounds and infections is shown even better 
in figure 3. The curve for wounds is plotted from Table IX, knots, 
of course, not being included, for had this been done the wound 
curve would have followed the 100 per cent ordinate throughout all 
the ages. The curves for infections and cull are the same as those 
given in figure 2. 
These curves show that infections are practically a function of 
wounds, the two curves having almost the same form, but of course 
the infection curve being lower throughout until both have attained 
100 per cent. The curve for the percentage of cull is included in 
