250 Minnesota Plant Diseases, 



evils of green lumber are here apparent, for infection takes 

 place more readily than in well-seasoned material. 



The preventive measures are indicated in the above ac- 

 count. The fruiting bodies should be destroyed as soon as they 

 appear. Well-seasoned wood is preferable to green wood. 

 The use of partially diseased wood is dangerous on account of 

 the probable spread of the disease to other timbers as well as 

 to the healthy parts of the diseased timber. Moist deadening 

 material of all kinds should be avoided as also such substances 

 which could create alkaline solutions in the presence of mois- 

 ture. Ventilation of large timbers is sometimes effected by 

 boring longitudinal holes through the center and transverse 

 connecting holes near the ends. In general, the formation of 

 stagnant, moisture-holding cavities should be avoided wherever 

 possible. (See also Fig. 5.) 



The false tinder-fungus rot[Fomes igniarius (L.) Fr.]. This 

 is one of the true pore fungi and is a dangerous and common 

 timber parasite. The plant gains entrance to the living stem 

 through the bark, usually at a wound or other opening which 

 may have been caused by such agencies as wind, hail, squirrels, 

 birds or boring insects. When the fungus has gained entrance 

 it attacks the growing portion of the stem, which is situated 

 just beneath the bark and it may establish here an extensive 

 mycelium. From this mycelium are later produced the shelf- 

 like fruiting bodies. The latter are usually half globular when 

 young, becoming hoof-shaped when older. The lower surface 

 is lined with a layer of pores which are white when young, be- 

 coming dark yellow-brown with age. New layers are added in 

 successive seasons. The upper surface of the fruiting body has 

 usually a very hard coat. Internally it consists of a softer 

 brownish felt-like material and numerous long tubes, which end 

 at the lower surface. The hard skin of the upper surface of the 

 fruiting body is usually cracked in older specimens. The wood 

 attacked by this mycelium undergoes a white rot. It first be- 

 comes dark in color, then as the process of disintegration con- 

 tinues it becomes yellowish to white. The fungus threads at- 

 tack the walls of the wood elements destroying their woody 

 characters and leaving them softer and lighter in color. The 

 chief danger of this fungus lies in the destructive parasitic habit 



