Page:Popular Science Monthly Volume 15.djvu/545

Rh 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 areæ, 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 appearing 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 external 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, discoloration, 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 decayed 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