48 FOREST TREE DISEASES. 



fruiting bodies are large, blackish on the upper side, 

 creamy white on the underside, and usually have a 

 broad reddish to chestnut-colored, shiny belt above 

 the light margin. On standing trees they are usu- 

 ally hoof-shaped. The underside is more or less 

 horizontal, smooth, with veiy small pores, and the 

 margin rounded. They vary considerably in shape, 

 however, according to where they appear. On the 

 underside of logs they may form rounded burls or 

 knobs, while on the upper side they occasionally ap- 

 pear in the form of short-stalked, broad toadstools. 

 The substance of the fruiting bodies, which shows dis- 

 tinct layers, is tough, stringy, later woody, and of a 

 very light yellow brown or isabel color. Drops of a 

 clear liquid often hang from the white underside of 

 the fruiting body. The fungus produces a very char- 

 acteristic red rot in the heartwood, with broad, white 

 felts of mycelium. It is exceedingly destructive to 

 fallen timber, and may cause damage to living trees as 

 well. On the other hand, it acts as a scavenger on 

 waste logs, which are transformed within a compara- 

 tively short time into a punky mass. This punky 

 wood, however, presents a serious fire menace. A sin- 

 gle spark will set it to smouldering for days or even 

 weeks until a strong wind fans it into a blaze. 



POLYPORTJS DRYOPHILUS. 



Polyporus dryvphilus is very common on living oaks. 

 The annual fruiting bodies are conspicuous, and either 

 grow on the side of the stem or limb, when they are 

 hoof-shaped, or else hang from the underside of the 



