1888-89.] On Dry-Rot. 247 



hyphse whicli it sends forth penetrate the wood. They soon 

 exhaust the cells of the medullary rays of their contents, the 

 nitrogen, potassium, and phosphorus of which are essential for 

 the growth of the fungus. They permeate the wood in all 

 directions, breaking up the substances, and appropriating those 

 required for the development of the plant. On the surface of 

 the timber little round patches like jewellers' wool first make 

 their appearance. These increase in size, and, meeting, form 

 a dense mass of interlaced material like felt, which covers the 

 beam like a carpet. This is the mycelium or vegetative part 

 of the fungus, and corresponds to the spawn of the mushroom. 

 The part analogous to the pileus or cap is of a stiff corky 

 nature, and lies next the beam. When the plant begins to 

 fructify, the mycelium takes a more definite outline ; it becomes 

 wrinkled and pitted on the surface, and of a spongy charac- 

 ter, having the walls of the depressions indented and zigzag. 

 These depressions form the hymenium, and correspond to the 

 gills of the mushroom. It now assumes a yellowish-brown 

 colour, distils drops of clear water, and sheds a ferruginous 

 powdery mass (the spores or seeds). A single fructification 

 will produce hundreds of millions of spores, each of which is 

 calculated to be about a 3000th part of an inch in diameter. 



Dry-rot prefers unpolished deal as a substratum on which 

 to develop itself. From wood the spawn spreads to walls of 

 stone and brick. It will go through the mortar, and develop 

 itself both inside and outside the wall. It has been observed 

 growing on plate-glass, maintaining itself there by means of 

 nourishment drawn from the wood. It is frequently found in 

 wine-cellars, from the woodwork of which it creeps along the 

 sawdust. It penetrates between the cork and the neck of 

 the bottle, imparting a " corky " flavour to the wine. Dry- 

 rot commits such rapid and deadly havoc in buildings, that it 

 is not inappropriately termed the Jewish leprosy in houses. 

 If the conditions are favourable when it attacks the wood- 

 work of buildings, it continues to gi^ow till the supporting 

 wood is completely exhausted, causing the floors and the roofs 

 sometimes to fall in. Cases of dry-rot in Edinburgh are more 

 common than people have any conception of. Shortly after 

 the opening of the Koyal Infirmary, dry-rot attacked the wood- 

 work of the wards, and tlae floors had to be replaced at great 



