490 Missouri Agricultural Report. 



Black locust, Kentucky coffee tree, catalpa, Osage orange, mul- 

 berry, black walnut and chestnut. 



Other good species have been used, but in many sections of 

 the country they are becoming too scarce or too expensive to be 

 used for this purpose. Substitutes must now take their place. 

 These may be in the form of iron or reinforced concrete, materials 

 which make posts too expensive, or else woods which decay more 

 rapidly than the ones formerly used. Such trees are as follows: 



Maple, ash, elm, hickory, red oaks, basswood, sycamore, birch, 

 Cottonwood and willow. 



There remain in the wood lots today many such species, which, 

 if given a proper preservative treatment, can be made to last 

 twenty years or more where they would otherwise decay in less 

 than five years. 



In order to clearly understand the principles involved in pre- 

 servative treatment, it is first necessary to know what causes decay 

 in wood. Decay in wood is caused chiefly by a low order of plant 

 life called "fungi." The "seeds" of these plants are called spores. 

 Spores are so small that they cannot be seen without the aid of a 

 microscope. When seen in bulk they appear as a fine dust, and, 

 like dust, they are carried by the wind and strike all parts of sur- 

 rounding objects. Like all plants, in order to exist, a fungus 

 must have a supply of food, water, air and a certain amount of 

 heat. If the requisites are found in the lodging places of these 

 spores — the fence post for example — they begin to grow. They 

 send out thin, film-like threads, which, by repeated branching, 

 penetrate all parts of the wood structure. Wood is made up of 

 small cells having thin cellulose walls. These thin walls are 

 thickened by lignin. Communication between these cells is by 

 means of pits. It is through these pits that the fungus sends its 

 "roots" — the film-like threads. A substance is secreted by these 

 "roots" which absorbs the food materials for the fungus. Some 

 fungi live on the sugars or starchy matter stored up in the wood, 

 others, the more formidable ones and the real wood destroyers, dis- 

 solve the cell walls and lignin, thereby changing the hard wood into 

 an incoherent mass of powder or dust. 



All woods which have a moisture content of over 10 per cent 

 are subject to decay. Fungi when cooled to near the freezing point 

 ceases activity but do not die; when heated to about 150° Fahren- 

 heit they are killed and so the wood is disinfected for the time 

 being. When wood is submerged in water or deeply buried the 



