4 BULLETIN 871, U. S. DEPARTMENT OF AGRICULTURE. 
Most important of all, however, is the loss of the present capital 
of timber through decay. The organisms causing decay in incense 
cedar are the pouch fungus (Polyporus volvatus) , Polystictus abietinus, 
Polystictus versicolor , Lenzites sepiaria, the red-belt Fomes (Fomes 
pinicola), some unknown fungi, and the incense-cedar dry-rot fungus 
(Polyporus amaru-s). The first five listed have never been found 
attacking living incense cedars. ■ There are several forms of decay 
of trifling importance in living trees, the causes of which have not 
been determined. Polyporus scliweinitzii has been found in one case. 
Standing out above all the other components of the total-loss 
factor is Polyporus amarus, causing dry-rot in the heartwood of the 
tree. Since the first utilization of incense cedar, the great destruc- 
tion wrought by this fungus has been a matter of extreme concern 
to lumbermen and foresters, as is shown by the constant references 
to the decay found throughout the literature wherever incense cedar 
is mentioned. 
The importance of dry-rot can not be overestimated, and it is on 
this point, together with the related mechanical injuries, that a study 
of the total-loss factor must be concentrated; the other considera- 
tions play a distinctly secondary role. 
METHOD OF COLLECTING DATA. 
SELECTION OF AREAS. 
The first step in carrying on a study of the total-loss factors in 
any given species is the selection of proper areas for work. The 
areas selected, if the results are to serve for any but strictly local 
application, must be representative of the larger unit or region of 
which they form a part. It is self-evident then that areas located 
in the altitudinal or horizontal extremes of the range of the species 
under investigation must be avoided. The results of a study on 
such areas, while scientifically interesting, would be absolutely with- 
out practical value, since they would only answer for a limited unit 
on which the stand is abnormal and would fail to answer any ques- 
tions in regard to the major and more valuable portion of the range 
of the species. 
All indications tend to show that there is a considerable variation 
in the growth and development of incense cedar in different parts 
of its range. This has already been hinted at by Mitchell (17, p. 9, 
13, 23, 24). The writer distinguishes three distinct ranges based 
on the development of the tree, and these are termed, for conve- 
nience, the optimum, intermediate, and extreme ranges. 
The best development is found in the southern Sierras, particularly 
on the Sierra, Sequoia, and Stanislaus National Forests, and the 
southern portion of the Eldorado National Forest, where the species 
is relatively rapid growing and thrifty. 
