DRY-ROT OF INCENSE CEDAR. 
33 
a strong bearing on the development of cull cases and the percentage 
of cull. 
Since neither the total number of infections nor cull cases follows 
the same law as the percentage of cull, it is self-evident that there 
must be an exact relation between this last and the more extensive 
or severe cull cases. Accordingly, in Table IV the severe cull cases, 
that is, those cases in which one- third or more of the total volume of 
the tree is a loss through dry-rot, are considered separately. The 
same basis is used as in Tables II and III and the percentages are 
based on the number of trees in the dominant and suppressed groups 
considered separately in each age class. 
Table IV. — Relation between dominant and suppressed trees in severe cull cases found in 
incense cedars of the combined areas. 
Age class. 
Severe cull cases (per 
cent). 
Age class. 
Severe cull cases (per 
cent). 
Dominant. 
Suppressed. 
Dominant. 
Suppressed. 
to 40 years 


2 
2 
14 
31 
48 
281 to 320 years. . . 
71 
67 
100 
66 
41 to 80 years 

3 
2 
5 
26 
73 
321 to360ryears... . 
81 
81 to 120 years 
361 to 400 years 
50 
121 to 160 years 
401 to 440 years 
100 
161 to 200 years 

201 to 240 years 
14 I 17 
241 to 280 years 
In Table IV is seen the same form of progression for the severe cull 
cases as was shown for the amount of cull in Table II. Low per- 
centages in both groups up to an age of 160 years, with a sudden 
increase in the percentage of severe cull cases in the age class of 161 to 
200 years for the suppressed group are followed by a like increase in 
the class of 201 to 240 years for the dominant trees. After 240 years 
is passed there is a higher percentage of severe cull cases for the sub- 
sequent age classes in the dominant group, just as is the case for the 
percentage of cull. The only exception to this is found in the class of 
321 to 360 years, where the relation is reversed. 
The outstanding fact shown by Tables II, III, and IV is that incense 
cedar during the earlier stages of its life, even though heavily infected, 
is able to retard the progress of the dry-rot fungus in causing decay. 
Then comes a period, earlier in the case of suppressed than of domi- 
nant trees, at which the progress of the fungus can no longer be held 
in check and the trees become subject to severe decay, with the accom- 
panying high percentage of cull. In other words, the decay becomes 
extensive. This period occurs in the age class of 161 to 200 years in 
the suppressed group and in the age class of 201 to 240 years in the 
dominant group. An analysis of the individual trees, in a table which 
is too long to present here, reveals the fact that this change begins at 
167 years in the suppressed and at 214 years in the dominant trees, 
