What You Should Know
Hymenochaete rubiginosa spreads and forms caps (effused-reflexed) on old logs and stumps, growing and producing spores for several years. Caps develop concentric zones of color and become very hard, breaking like a thin seashell. The fertile (spore-producing) surface is orange-brown and covered with tiny, bristle-like spines (setae). Previously misidentified here as Pseudochaete tabacina.
Widespread in most of mainland Europe.
Other names: Oak Curtain-Crust.
Hymenochaete rubiginosa Mushroom Identification
Upper (infertile) surface
Perennial fruit bodies are irregularly oval with wavy margins; 2-4cm across and concentrically ridged on the upper surface, which feels finely velvety (it is covered in finely pointed hairs, visible with a good hand lens). The infertile surface is dark brown, except for the growing margin which is noticeably paler.
Sometimes the fruit bodies are largely resupinate, while on occasion they can form shelf-like brackets.
Lower (fertile) surface
The fertile surface is mainly smooth but often with a few scattered warty lumps or short warty ridges. Orange-brown when young, the fertile surface eventually darkens to a grayish red-brown.
Ellipsoidal, smooth, 4.5-6 x 2.5-3μm; inamyloid.
Odor and Taste
Habitat & Ecological Role
On fallen timber of dead hardwood trees, nearly always oaks and most commonly appearing at an exposed surface where a fracture has occurred or the bark has fallen or rotted away.
Alder Bracket Inonotus radiatus produces paler fruitbodies and weeps honey-colored droplets; as the common name implies it is found mainly on the basal roots and lower trunks of alder trees.
Hymenochaete rubiginosa Taxonomy and Etymology
In 1785, Scottish botanist-mycologist James J Dickson (1738 - 1822) described Oak Curtain Crust fungus, he gave it the name Helvella rubiginosa. Helvella fungi are ascomycetes, but the distinction was not clear in those pioneering days of fungal taxonomy. Dickson retains credit for the basionym, but the generally-accepted scientific name for this corticioid basidiomycete fungus is now Hymenochaete rubiginosa, this name having been given to it in 1846 by French mycologist Joseph-Henri Léveillé (1796 - 1870).
Synonyms of Hymenochaete rubiginosa include Helvella rubiginosa Dicks., Auricularia ferruginea Bull., Stereum ferrugineum (Bull.) Gray, Stereum rubiginosum (Dicks.) Gray, and Hymenochaete ferruginea (Bull.) Massee.
Hymenochaete, the genus name, comes from hymen- a prefix referring to the fertile membrane (the crust surface), and -chaete perhaps from the Greek noun chaite meaning long hair and perhaps referring to the fine hairs (settae) on the upper surfaces of fungi in this generic group.
The specific epithet rubiginosa means rusty and refers to the reddish-brown color of the hymenial (fertile) surface of this crust fungus.
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