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 (Forties 

 pinicola), some unknown fungi, and the incense-cedar dry-rot fungus 

 (Polyporus amarus). 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 schweinitzii 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 r61e. 



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. 



