200 PLANT DISEASES 



luminous account of this fungus given by Hartig will be 

 of value. 



Wood that is perfectly sound when felled may become 

 diseased even before leaving the forest, especially in the 

 case of peeled trees lying on the ground. During drying, 

 the wood cracks, and spores often enter these cracks, which 

 close up when the wood is thoroughly wetted, enclosing the 

 spores. These germinate and attack the woody tissues, 

 and too frequently continue their work until the wood is 

 used, when, if conditions are favourable, the well-known 

 ' dry rot ' soon makes its presence evident. 



If fungus mycelium is present in wood used for structural 

 purposes, and any portion comes in contact with moisture, 

 as the ends of joists joining a damp wall, the mycelium 

 soon commences to grow actively. The use of damp 

 sound-deadening material is very productive of ' dry rot ' ; 

 clean dry gravel or coarse dry sand is best; and on no 

 account use coal-dust, cinders, or any other substance 

 capable of forming an alkaline solution with moisture, as 

 the spores only germinate in an alkaline solution. 



If 'red-stripe' wood is used for beams, etc., the ends 

 likely to come in contact with damp walls, etc., it should be 

 thoroughly treated with creosote. * Red-stripe ' is the early 

 stage of an attack by the mycelium of ' dry rot,' and it is 

 far better not to use such in buildings ; but as this is con- 

 stantly done, the next best thing is to use creosote or 

 some other material that will prevent the spread of the 

 disease. 



The fungus first appears as a thin white film of mycelium, 

 and gradually becomes thicker at the centre, where it 

 assumes an irregularly porous structure, and changes to 

 a rich rusty-brown colour; the substance is soft, and the 



