364 SCIENCE PROGRESS 



stated that every wood-destroying fungus consists of two parts, 

 a vegetative and a reproductive. The vegetative is known as 

 the mycelium, which is very much branched and made up of very 

 fine threads or hyphce. These penetrate in all directions into the 

 cells of the wood and cause it to go rotten. Such decayed wood 

 is often known popularly as "touchwood." The reproductive 

 part of the fungus develops on the outside of the rotting wood. 

 It is known as a sporophore, or fruit-body. It is devoted 

 exclusively to the production and liberation of spores, and is 

 developed entirely at the expense of the food obtained by the 

 mycelium hidden in the wood. Some fruit-bodies are very large 

 and form brackets or hoof-shaped masses of various hues. 

 When projecting from tree-trunks or logs they may attract 

 the attention of the least observant. 



The Ascomycetes rarely do much damage to the wood in 

 bulk, such as tree-trunks or thick branches. They are numerous, 

 however, upon twigs and the surface of wood. They require a 

 comparatively small amount of food to produce their small 

 fruit-bodies. 



The Basidiomycetes are the most active destroyers of wood. 

 The lower forms have comparatively simple fruit-bodies, and are 

 often found on small branches. The higher forms, however, 

 have more complex and, as a rule, much more massive fruit- 

 bodies. When wood is the food, this is obtained by acting with 

 enzymes upon the substance of thick branches and tree-trunks. 

 In this manner the Basidiomycetes remove most ol the wood 

 which falls to the floor of our forests. 



It is admitted that if timber be kept perfectly dry, or sub- 

 merged beneath water, it will resist decay for an indefinite 

 period. It was formerly thought that alternate exposure to air 

 and water was sufficient per se to bring about the decay of wood. 

 There is, however, no evidence that such is the case in the 

 absence of living organisms. 



The causes which lead to the decay of wood were elucidated 

 toward the latter end of the nineteenth century. Just three 

 decades have passed since the publication of Robert Hartig's 

 classical researches. 



Theodore Hartig, 1 father of Robert Hartig and the discoverer 

 of sieve-tubes and aleurone grains, was the first to investigate 

 the destruction of wood by fungi in a scientific manner, and 



1 T. Hartig, Berlin. 



