52 FOREST TREE DISEASES. 



The advance rot extends about 2 to G linear feet beyond 

 the unmistakably decayed timber; in scaling, it should 

 be treated as cull. Besides white fir, the fungus may 

 also attack Douglas fir, and occasionally red fir. It is 

 often connected with cankers caused by Razoumofskya 

 occidentalis (p. 58). 



HYDNUM ERINACEUS. 



This fungus is sometimes found on oaks. The large, 

 head-shaped, annual fruiting bodies are white, very 

 fleshy and juicy when fresh, but later dry up to small 

 brown or blackish masses. They are often destroyed by 

 insects. Soft, white spines or teeth cover almost the 

 entire fruiting body. In the course of the disease the 

 heartwood of the tree becomes lighter in color, finally 

 appearing almost white, and is rapidly and completely 

 destroyed. The stems of oaks affected with this rot 

 often consist of but a hollow shell of sapwood. 



HONEY FUNGUS. 



The honey fungus (Armillaria mellea, Pis. XIX and 

 XX) is one of the most destructive root fungi of oaks 

 and orchard trees (oranges, apricots). In our forests 

 it does not appear to be very common, but it is likely 

 to spread. It may attack coniferous trees (sugar pine, 

 white fir) of all ages, often spreading through dis- 

 eased roots to roots of sound neighboring trees, which 

 it kills in a short time. The butt of affected conifer- 

 ous trees often shows a heavy outflow of resin. Con- 



