42 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. 



To reduce the figures in column 5 of Table I to simpler symbols 

 was more difficult. Here the entire affected part of the cone for 

 practical purposes was considered as cull, including the sap wood. 

 In reality, there are, of course, all gradations from a slight discolora- 

 tion of the sapwood following a long lightning scar or a number of 

 smaller scars to complete destruction of the heartwood by decay. 

 In order to simplify this column and to bring out more forcibly its 

 relation to influencing factors, the writer tried to reduce the percent- 

 age figures to ratings, applying the system of crosses used throughout 

 this study, taking into account ftot only the volume percentage of rot 

 in cubic feet, but also the character of the injury with regard to the 

 degree of rottenness. Thus, one cross in parentheses, (x), signifies 

 slight and negligible local discoloration; one cross (not in parentheses) 

 shows distinct rot, but affecting not more than about one-third of 

 the tree; two crosses, about two-thirds of tree affected; three crosses, 

 more or less of the entire tree affected. In each case, the character 

 of the decay as indicated by the detailed field notes was given due 

 consideration. This explains apparent discrepancies between decay 

 rating and decay volume in the percentages in Table I, where the 

 affected part of the bole was considered as cull for the entire length 

 of the decay. In decay rating, the actual loss in merchantability 

 was expressed according to the character of the rot and its extent. 

 This valuation of the decay, it is true, is necessarily somewhat arbi- 

 trary. It is really the condensation of carefulty taken field notes and 

 measurements and must serve until a more satisfactory method can 

 be found. Where general relationships only are concerned, as in 

 this case, our symbols may be sufficiently correct, provided they are 

 based on exact figures and reliable field notes. (Table II, column 6.) 



In order to insure a higher degree of reliability for the decay-rating 

 symbols, the operation was repeated some time later without con- 

 sulting the results of the first. With insignificant exceptions, both 

 ratings were identical. 



In much the same way the character and degree of wounding was 

 reduced to a system of crosses. Plainly, this can be done only from 

 field notes, which were generally amplified by actual measurements 

 of the size and extent of the wound. The chances of inoculation 

 offered by a wound decide its rating. That deep wounds, particu- 

 larly such as have remained open for a longer time, are rated higher 

 than small superficial injuries, soon healed over, is self-evident. The 

 system of crosses is the same as heretofore explained. (Table II, col- 

 umn 7.) 



The next column (Table II, column 8) indicates the means whereby 

 the fungus entered the tree, as evidenced by the analysis. 



