DRY-ROT IN TIMBER. 529 



upon the white mycelium. In this fungus the stem is entirely absent, 

 and the cap is attached by its back. In the different species we may 

 find the reproductive or spore-bearing portion in the form of a cup, 

 or a goblet, or a saucer ; of an ear, a bird's nest, a horn, a bunch of 

 coral, a button, a rosette, a lump of jelly, or a piece of velvet. The 

 Merulius is found in cellars and hollow trees, sometimes several feet 

 in width. 



Another fungus, the Polyporus hybridus, is an especial enemy of 

 oak-timber. It is described by Berkley as " white, mycelium thick, 

 forming a dense membrane or creeping branched strings ; hymenium 

 breaking up into areae, pores long, slender, minute." This species makes 

 great havoc in the navy. At one time it is said, in the memoirs of 

 Pepys, thirty new wooden ships in the British navy, "for want of 

 proper care and attention, had toadstools growing in their holds as v big 

 as one's fists, and were so decayed that the planks dropped from their 

 sides." In the beginning of this century, three 74-gun ships of the 

 Royal Navy decayed in five years ; three others in seven years ; and 

 a 100-gun ship in six years. Fungi have been seen growing between 

 the timbers of a man-of-war strong enough to force a plank half an 

 inch from the ship's side. 



But, without attempting to discriminate among the fungi causing 

 dry-rot, it may be stated generally that, in timber that has been only 

 superficially seasoned, this disease often arises internally, and has been 

 known to convert the entire substance of a beam, excepting an inch or 

 two at the surface, into fine, white, and thread-like vegetation, which 

 forms a thick, fungous coat at the ends of the beam, otherwise appear- 

 ing perfectly sound. This has often been observed in large girders of 

 yellow fir, which have seemed sound on the outside. Major Jones, 

 R. E., states of a building in Malta, that " the timbers had every ex- 

 ternal appearance of being sound, but on being bored with an auger 

 they were found internally in a total state of decay." 



The first symptoms of dry-rot in timber are swelling, discolora- 

 tion, moldiness, and a musty smell. As the disease advances the fibers 

 shrink lengthwise and break, presenting many deep fissures across the 

 wood ; finally, the cohesion of the wood is utterly destroyed, and at 

 the least disturbance it crumbles to powder. Before it has time to 

 destroy the principal timbers in a house, it gets behind the skirtings, 

 dadoes, and wainscotings, drawing in the edges of the boards, and 

 splitting them both horizontally and vertically. When cleared of the 

 fungus they look like wood that has been charred. Though affected 

 but a short time, a slight pressure will break them asunder : and, when 

 examined, the fibrous fungus will be seen closely attached to the de- 

 cayed wood. 



Timber that is floated down rivers and conveyed from place to 

 place in ships is very liable to this disease. It is said of the exports 

 of timber from Canada to England, that few cargoes in the log arrive 

 vol. xv. 34 



