Any of various fungi that form shelflike growths on tree trunks and wood structures. Also called shelf fungus. or shelf fungus Basidiomycete that forms shelflike sporophores (spore-producing organs). Bracket fungi are commonly found growing on trees or fallen logs in damp woodlands. They can severely damage cut lumber and stands of timber. Specimens 16 in. (40 cm) or more in diameter are not uncommon