POLYPORUS SCHWEINITZII, FR. 57 



roots which are comparatively near the surface of the ground. 

 Evidently the fungus first attacks the roots and then 

 gradually works upwards into the trunk. There it spreads, 

 causing decay in the stem which has been known to reach a 

 height of 40 to 50 feet. 



The rot produced is rather characteristic. At first the 

 wood becomes dull yellow, later it changes to dark brown. 

 Here and there small white patches or pockets of mycelium 

 may be seen. The whole mass becomes brittle, very light, 

 and is broken up by many fissures. Occasionally, the sides 

 of the fissures are coated with a thin, chalky, non-branching 

 mycelium. Spiral cracks and fissures, said to be due to the 

 drying and shrinkage of the wall substance, make their 

 appearance in the tracheids. The decaying wood has a 

 turpentine-like odour. 



The rate at which the fungus progresses seems to be variable. 

 About six years ago a large Sitka spruce first produced sporo- 

 phores at a few feet from the base of the trunk. To outward 

 appearance the tree remained healthy till it was broken over 

 by wind two years ago. The outer wood, to about 6 or 

 8 inches in width, was then found to be the only sound 

 part in a butt 3 feet in diameter at breast-height. About 

 18 feet of the stem showed more or less distinct signs of rot. 



A Douglas fir bore one fructification eleven years ago 

 Other single ones came up in the next two years, and since 

 then none have appeared. This may or may not mean that 

 the fungus is now dead. At present other attacked Douglas 

 firs are under observation, and on some of these, large and 

 apparently vigorous sporophores have been produced for 

 several years. As yet I have not seen the wood of an aff"ected 

 Douglas fir, and therefore cannot say what the effect of the 

 fungus is on it. 



The following remedial and preventive measures might be 

 suggested: — (i) Cut off affected roots well above the place 

 where the last sign of rot appears, and tar the wound ; 

 (2) Collect and burn sporophores while young; (3) Cut out 

 badly attacked trees and plant hardwoods in their places. 



