The Durability and Preservation of Woods 243 



have some cheaper species here, and all species are of 

 equal durability when treated. 



CAUSE OF ROT 



What is generally known as rot in wood is the result of 

 a low form of vegetable or fungous growth. There are 

 thousands of species of these plants, but as they are all 

 parasitic and have practically the same development, a 

 brief, general life history will answer for all of them. 



The spore, or egg, from which this plant develops is 

 almost, in some cases wholly, invisible to the naked eye. 

 They are carried about by the wind in countless numbers. 

 The vast majority of them fall in unsuitable locations and 

 die, but some of them, finding openings in trees and logs, 

 begin their own development to the destruction of the host 

 on which they are growing. They usually take up their 

 positions in a dead tree or log, but occasionally make their 

 way into some live vigorous tree the bark of which has 

 been broken by a wind storm, a poor job of pruning, or 

 some other injury. 



Once the spore has found lodgment in a favorable local- 

 ity, it begins a very rapid development. Mycelia, long, 

 white, threadlike filaments, penetrate the cell walls and fill 

 up the interior of the cells. In this way the life of the cell 

 is destroyed, and the substance of the wood becomes food 

 for the fungus. The growth of the plant is indeterminate 

 and so many cells of the wood are destroyed that the host 

 itself finally gives up the struggle and dies, thus giving 

 itself up wholly to the myriad of weaker fungi and insects 

 that attack a dead or dying tree. 



When the fungus has reached the proper stage of develop- 



