THE EOTS OF WESTERIf WHITE PI]SrE. 15 



for the bottom sites. This is clue principally to the larger number of 

 basal fire scars recorded for the trees on the slopes. On both types 

 of site a steady increase of the total number of trees with injuries is 

 recorded, ranging on the bottom sites from in the 41 to 60 age class 

 to 97 per cent in the 201+ class. On the slope sites the percentage 

 ranges from in the 41 to 60 age class to 99 per cent in the 201 -|- 

 class. Coniparing the entire stand of each type of site it is seen that 

 the percentage of total trees infected is 55 on the bottom sites and 

 55.3 on the slope sites. A more correct comparison of the amount of 

 injury found in the stands of each type of site is made by con- 

 trasting the percentages of total trees, both sound and infected, bear- 

 ing injuries. For the bottom sites this percentage is 90 and for "the 

 slope sites 70, indicating that a larger number of trees on the bottom 

 sites bore injuries. This difference may be partly due to the presence 

 of a larger number of branch stubs on the trees of the bottom sites. 

 These data clearly indicate the increasing danger of infection through 

 injuries with the increase in age for both sites. 



From a study of Table V it appears that frost cracks as sources of 

 infection are more common in the older age classes and not present 

 at all in the younger. The recorded field data show that frost cracks 

 were more frequent in the older trees, which accounts for the pre- 

 ceding statement. 



The degree of injury for the two types of site shows a fairly steady 

 increase with increased age and a slight difference in degree of injury 

 for the total stand of the two tj'pes of site. The bottom sites have 

 but a few tenths greater degree of injury. 



Table V shows that 10 to 30 per cent of the trees are without in- 

 juries. These trees are principally in the youngest age classes and 

 bear no dead branches. 



SPOROPHORES. 



Most of the sporophores encountered in the western white-pine study 

 were those of Trcmietes pini. Very few sporophores of Polyponis 

 schweinitzii or of Fomes annosus were found attached to the trees. 

 Most of the PolypcyrUfS schweinitzii fruiting bodies developed on the 

 ground at the base or near the host, and the logging operations 

 nearly always disturbed these from their original positions. A very 

 few sporophores of Polyporus schweinitzii were found attached di- 

 rectlj^ to the base of the tree. The data in Table VI, therefore, are 

 principally from field notes on one fungus, Trametes pini. In this 

 table it will be noted that the 41 to 60 age class is omitted, since no 

 rot and therefore no sporophores were present on the trees of this 

 class. On the bottom sites out of a total of 533 trees aj)proximately 

 30 per cent were found bearing sporophores. On these sporophore- 

 bearing trees a total of 604 sporophores were recorded, of which 561, 



