366 DISEASES OF CULTIVATED PLANTS 



originally dry-wood which, after it has been disorganised, 

 becomes dry and rotten, hence the common name of ' dry- 

 rot.' The fruiting portion of the fungus is a thickish, felt-like 

 patch of variable size, from four to eight inches across, and 

 is attached throughout by its under surface to the substance 

 it is growing upon. The upper spore-bearing surface is 

 covered with slightly raised ribs anastomosing to form an 

 irregular network ; it has been compared in general appearance 

 to a piece of tripe. When the spores are ripe the hymenium 

 is of a deep brown or snuff colour, and powdery. Spores 

 elliptical, bright brown, 10-11-5-6 //,. The margin of the 

 hymenium consists of white mycelium which in a vigorously 

 growing specimen resembles cotton wool. This marginal 

 portion keeps extending outwards and adding to the size of 

 the hymenium. When the fungus becomes old the white 

 mycelium changes to a dull grey colour. The entire fungus 

 can be readily removed from its support, and presents the 

 appearance of a thick sheet of felt or leather. Under certain 

 conditions the entire hymenium remains sterile, and of a 

 dirty grey colour. 



When a dry-rot fungus has become well established, 

 numerous strands and flat plates of mycelium, white at first, 

 then greyish, spread out from every part of the white margin 

 of the hymenium. These strands grow along walls or what- 

 ever kind of support happens to be forthcoming, being 

 supplied with food and moisture from the parent plant. 

 When wood is reached by any of these strands, a new head- 

 quarter is formed, and a new hymenium is produced, from 

 which strands of mycelium again emanate and extend in 

 every available direction until more wood is reached, when 

 the process of forming a new centre of food supply is carried 

 out. By these means, if dry-rot once gains admission to a 

 house, it is possible for it to reach every part from basement 

 to attic. 



Infection of wood often takes place in the forest, when 

 felled timber remains stored there for some time. The 

 earliest evidence of infection is indicated by the presence of 

 red stripes in the wood. If such timber is afterwards 

 thoroughly seasoned and dried the mycelium of dry-rot in 

 the red stripes is killed, but if the seasoning is only imper- 

 fectly carried out, as is usual at the present day, the fungus 

 mycelium remains latent, and may begin active growth 

 if the wood is placed in a damp, badly ventilated part of a 



