Minnesota Plant Diseases. 



245 



Dry rot or house fungus rot [Merulius lacrymans (Wulf.} 

 S churn.']. This fungus is one of the most destructive of timber 

 rots both on ac- 



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count of its action 

 and its frequent oc- 

 currence. It is one 

 of the simplest of 

 the pore fungi, hav- 

 ing only shallow 

 pores on a flat pros- 

 trate fruiting body. 

 It may almost be 

 termed a domesti- 

 cated fungus for it 

 appears almost ex- 

 clusively in the 

 neighborhood 

 of dwellings and is 

 very seldom seen 

 native in the woods. 

 It has therefore been 

 called by the Ger- 

 m a n s "h a u s- 

 schwamm" or house 

 fungus. It is also 

 popularly known as 

 the weeping fungus. 

 It attacks chiefly the 

 soft woods of needle 

 trees but may also 

 destroy oak and 

 other hard woods. This fungus is a typical saprophyte and de- 

 rives its nourishment from the wood which it destroys. When 

 the mycelium has permeated a wood tissue it leaves the latter 

 as a spongy mass of brownish material, a common condition in 

 timbers which are kept in moist places. Such decayed wood 

 absorbs water readily and retains it so that the wood holds its 

 original size and shape, but when dry the decayed portions 

 shrink, causing cracks which form at right angles to each other, 



Fie. 120. The fruiting body of the dry rot fungus 

 ( Merulius lacrymans). The under surface covered 

 with shallow |>ores is shown in the photograph. Much 

 reduced. Original. 



