DRY-ROT OF INCENSE CEDAR. 21 



tree which was cut in 1915. The fungus entered through a healed 

 fire scar which occurred in 1781 and was completely closed by callus- 

 ing in 1816. By subtracting 1781 and then 1816 from 1915 it is 

 seen that the fungus has been in the heartwood a minimum of 99 

 and a maximum of 134 years. During this period resulting decay 

 has progressed a vertical distance of 34.2 feet in the bole, or a yearly 

 average of 0.25 to 0.34 of a foot. The radial extent of the decay is 

 disregarded, since this is of little importance from a practical view- 

 point. Any serious infection usually extends more or less through- 

 out the heartwood in a radial direction. Of course, the above 

 method does not give a single figure for the yearly average progress 

 of the dry-rot, but it does give the exact minimum and maximum 

 limits between which the true figure lies. 



In all 99 infections were possible of analysis by this method. 

 The great majority of these commenced at ground level, entering 

 through fire scars and extending up the bole. Ten of the infections 

 were traced to wounds high enough up on the trunk, however, to 

 make possible a comparison of the upward and downward progress 

 of the dry-rot. This meager basis indicated that the dry-rot, in the 

 main, progresses more rapidly downward than upward, although 

 in individual cases this relation may be reversed. 



The yearly progress of the decay is exceedingly variable. At one 

 extreme there is a tree in which the fungus had been vegetating be- 

 tween 124 and 135 years, but the resulting dry-rot had only attained 

 a length of 0.4 of a foot, or a minimum average yearly progress of 

 0.002 and a maximum of 0.003 of a foot. The tree was 147 years 

 old. At the other extreme, the fungus in from 10 to 58 years caused 

 decay extending over 30.9 feet of the bole of another tree, that is, a 

 minimum average progress of 0.53 of a foot a year and a maximum 

 of 3.09 feet. This tree was 240 years old. Again, in a 107-year-old 

 tree the fungus caused a decay with a minimum average progress 

 of 0.87 of a foot and a maximum of 1.90 feet a year, extending a 

 total of 40 feet vertically. In the main, however, the minimum prog- 

 ress of the dry-rot varied from 0.01 to 0.20 of a foot a year, while the 

 maximum ranged from 0.01 to 0.35 of a foot. Higher yearly rates 

 than the upper limits stated were not uncommon, but lower rates 

 than 0.01 of a foot were rare. « 



These figures clearly demonstrate the slow progress of the dry-rot 

 fungus in causing decay. Generally it required from 50 to 300 years 

 to bring about any far-reaching dry-rot. In the heartwood of cer- 

 tain individuals the fungus had vegetated for decades, the resulting 

 decay only extending 1 or 2 feet from the point of infection. A 

 similar condition was found by Munch (loc. cit.) for Poly porus (Fomes) 

 igniarius attacking oak. As to why the development of the dry-rot 

 fungus in certain cases is so inhibited the writer is unable to present 



