4 THE DECAY OF TIES IN STORAGE 



,'thi- ;deVu1.ripment and spread of wood-destroying fungi, to which we 

 attribute all the primary decays with which we are concerned. 



What Are Fungi? 



Fungi are plants, just as much as trees, shrubs and herbs. They 

 merely differ in their form, lack of green coloring matter, and methods 

 of nutrition. A tree gets its nutriment from the soil and air through 

 its root system and leaves ; the fungus derives its nutriment from the 

 substrate upon which it grows, namely, wood or other vegetable matter. 



In the life cycle of wood-inhabiting fungi we recognize two essen- 

 tial stages in development: (1) The 'mycelium (vegetative stage), which 

 consists of fine, cotton-like branched threads which penetrate the wood 

 and may also develop on the surface if the surrounding air be moist; 

 (2) the fruiting stage, which produces spores at the surface of the 

 timber. These spores may be found directly on the exposed mycelium, 

 as in the case of "molds," but more often they are produced on definite 

 fruit-bodies which are nothing more than mycelium compacted into 

 characteristic shapes representative of different fungi. 



Many fungi are wood inhabiting, but these may not all necessarily 

 be wood destroying. For practical purposes it is, therefore, necessary 

 to discriminate between two broad groups, namely, molds or stains and 

 wood destroyers. 



Mycelium 



The mycelium is the stage which penetrates the wood. It is the 

 absorbing system of the fungus and in function is comparable to the 

 root system of ordinary green plants. In the case of "molds" and 

 "blue stains," it mainly enters the ducts or pith rays of the wood where 

 it feeds on the starches, sugars and other easily digested organic com- 

 pounds. In the case of these fungi it may also pass through the pits 

 in the walls of the wood fibers, but rarely bores through the solid 

 wood substance. For this reason the molds and blue stain do not affect 

 the strength of the timber to any appreciable degree. 



The mycelium of both wood destroyers and molds is in many cases 

 colorless and rather fine when growing within the wood; that of the 

 blue stain is brown and usually coarse. The main difference between 

 the mycelium of wood destroyers, molds and blue stain, however, is 

 its action on the wood fiber, the wood destroyers having the capacity 

 to attack and disintegrate the wood substance itself while the molds 

 and blue stain act only on the starches, sugars and other organic sub- 

 stances stored in the pith rays and ducts. 



The chemistry of wood is rather complex, but the main constituents 

 of the wood substance itself are cellulose and ligno-cellulose (often 

 termed lignin), and any fungi which have the ability to feed on these 

 substances are necessarily wood destroying. These compounds, as 

 well as others in the wood, are acted on by specific ferments (enzymes) 



