Peniophora quercina is a species of wood-decay fungus in the family Peniophoraceae. It produces fruit bodies that vary in appearance depending on whether they are wet or dry. The wet fruit bodies are waxy and lilac, and attached strongly to the wood on which they grow. When dry, the edges curl up and reveal the dark underside, while the surface becomes crusty and pink. P. quercina is the type species of the genus Peniophora, with the species being reclassified as a member of the genus upon the latter's creation by Mordecai Cubitt Cooke. P. quercina is found primarily in Europe, where it can be encountered all year. Though primarily growing upon dead wood, especially oak, it is also capable of growing upon still-living wood. Taxonomy Early descriptions of the species came from Carl Ludwig Willdenow, who named it Lichen carneus in 1787, and Jean Baptiste François Pierre Bulliard, who, in 1790, named it Auricularia corticalis. However, the sanctioned name is Thelephora quercina, given by Christiaan Hendrik Persoon in 1801, and sanctioned by Elias Magnus Fries in the first volume of his Systema Mycologicum. The specific name quercina is in reference to Quercus, the generic name for oak. A number of authors (including Jean-Baptiste Lamarck, Lucien Quélet and Giacomo Bresadola) reclassified Bulliard's Auricularia corticalis throughout the 19th century, while Persoon's Thelephora quercina was reclassified by Samuel Frederick Gray in 1821, who placed it in Corticium as Corticium quercinum. However, in 1879, Mordecai Cubitt Cooke transferred the species to his newly described genus Peniophora, declaring it the type species. Despite subsequent attempts at reclassification, Cooke's name is the one currently used. Description Peniophora quercina produces resupinate fruit bodies that vary in appearance depending on whether they are wet or dry. They are up to thick, and form irregular patches that sometimes measure several centimetres across. Initially, the species forms small, disc-shaped fruit bodies through holes in bark, but these expand and merge to form the irregular patches. When fresh, the surface is reminiscent of jelly or wax, and can be smooth or warty, varying in colour from a dull blue to lilac. Initially, they are firmly attached to the wood on which they are growing, but as they dry, the edges roll inwards and reveal the dark brown or black underside. The dry specimens have a crusty and slightly fissured surface, and, in colour, are a bright pink or grey, tinted with