Serpula lacrymans (Fr.) Karst. syn. Merulius lacrymans Schum. Hausschwamm Dry Rot. Fruit body 5–50cm across, usually resupinate but occasionally forming brackets on vertical substrates, arising from whitish, pinkish, lilac or grey mycelium. Flesh 2–12mm thick, greyish-white, spongy-fleshy. Pores rusty-yellow becoming more yellowish towards the thick, white sterile margin. Spores rust-brown, elliptic, 8–10 x 5–6um. The fungus gives off a distinctive damp rotten smell. Habitat on worked wood in buildings although the fruit bodies of the fungus may also appear on non-organic substrates such as plaster or brickwork. Season all year. Common. Not edible. Distribution, America and Europe.
Infection of wood occurs when it has become sodden for some long time following prolonged damp due to leaking roofs or pipes, either by spores or by vegetative mycelium spreading through brickwork. On germination of the spores the mycelia exhibit two distinct modes of growth. Firstly, numerous fine hyphae penetrate the wood, producing enzymes which break down the wood and enable the fungus to absorb nutrients; as the wood dries it cracks into cubical blocks and eventually disintegrates into brown powder. It is the second mode of growth which is most easily detected since it takes the form of thick mycelial cords and cottony sheets spreading over brickwork, metal, etc. enabling the fungus to travel over areas from which it cannot derive nutrients. The fruit bodies arise from these mycelial cords. Thios phoyograph was lent to me by Alan and Patie Outen.