INSECTS, DISEASES, AND INJURIES 151 



into the wood. Here it continues to grow and causes the wood 

 to disintegrate in a typical manner. Usually no external 

 evidence of the disease is apparent until the fruiting structures 

 (sporophores) of the fungi appear on the injured part, and 

 this does not occur until one or more years after infection. 

 By that time one may generally consider that the rotting of 

 the wood is well advanced. 



The fruiting structures of the polypores are commonly 

 known as "punks" and usually project as bracket-like bodies 

 from the surface of the tree (Fig. 18). In some cases they may 

 appear as sheets more or less appressed to the surface. The 

 under side of these bodies is covered with minute pores which 

 are the openings to tubes. Within these tubes millions of 

 spores are produced, which at maturity are shed through the 

 openings. When the sporophores arise near the base of the 

 tree, one may often see the ground covered by a thick brown 

 dust made up of these spores. The wind carries them to 

 other trees, where fresh infections may be initiated. 



In the case of the toadstool referred to above, the sporo- 

 phores arise from exposed or superficial roots or as clusters 

 around the base of the tree. They possess a stalk and a cap 

 which is honey-yellow in color and for this reason the fungus 

 is often called the honey-mushroom. The stalk is somewhat 

 swollen at the base and just below the cap it is encircled by a 

 fragile collar. The spores are produced on the sides of plates 

 or gills on the under surface of the cap (Fig. 19). The base of 

 the stalk is connected with the tree roots by means of round 

 black strands which have the appearance of shoe-strings. 

 These grow through the soil from the roots of one tree to those 

 of another, penetrate the bark and produce infection. Spores 

 may also cause infection through wounds at the base of the 

 tree or in exposed roots. 



