THE ROTS OF WESTERN WHITE PINE. 19 



On the bottom sites it is observed that sporophores are recorded for 

 all the age classes, including that of 61 to 80 years. In the slope sites 

 both the 61 to 80 and the 81 to 100 age classes have no sporophores 

 recorded. The first sporophores appear in the 101 to 120 age class. 

 They increase in number in the 121 to 160 age class and decline in the 

 161 to 200 and the 201+ age classes. The column indicating the 

 average number of sporophores per tree indicates this very clearly. 

 The column recording the number of sporophore-bearing trees shows 

 a similar increase, reaching a maximum in the 121 to 160 age class, 

 and a rapid decline is noted in the two succeeding age classes. These 

 data indicate a maximum of sporophore production attained in 

 the 121 to 160 age class and show the rapidly decreasing numbers of 

 sporophores present on the trees of the two oldest age classes. Two 

 factors are responsible for the decline — first, the fact that the fungus 

 in the tree has reached and passed its maximum development and so 

 produced fewer new sporophores, and second, the fact that in the 

 old-age classes the old sporophores are observed to have died, be- 

 come loosened from the trunk, and dropped off. The relation of rot 

 percentage to sporophores is evident when compared on a basis of 

 site. On the bottom sites the rot percentage is nearly 8 (7.8, Table I) , 

 and an average of 1.1 sporophore per tree or 11 sporophores to every 

 10 trees is recorded. In the slope site the rot percentage is over 6 

 (6.1, Table I), and the average number of sporophores per tree is 

 0.8 or 8 sporophores to every 10 trees. The bottom sites show a 

 greater rot percentage and a greater average number of sporophores 

 per tree. 



Another interesting point brought out by the table is the fact that 

 on both types of site the smallest groupings of sporophores were 

 found on the southeast side of the trees. 



DISCUSSION OF RESULTS. 



From the foregoing data it appears that age is the important factor 

 in determining the amount of rot to be expected in a western white- 

 pine stand. This factor of age is significant in the application of 

 proper silvicultural methods to the care and disposal of the timber. 

 From the forester's point of view two things stand out in consider- 

 ing the stand in relation to rots. The one is the age of earliest infec- 

 tion of the stand, or the period when infection by fungi can first be 

 expected. This is undoubtedly controlled by the formation of heart- 

 wood and the appearance of injuries susceptible to infection. This 

 infection age is found to be approximately 60 years for western white 

 pine, and it indicates the period when the young stand is in need of 

 the utmost protection against infection by fungous spores. Infection 

 takes place in this tree earlier than at 50 years in certain individuals. 



