Urnula Craterium

''Urnula craterium'' is a species of cup fungus in the family Sarcosomataceae. It is parasitic on oak and various other hardwood species; it is also saprobic, as the fruit bodies develop on dead wood after it has fallen to the ground. Appearing in early spring, its distinctive goblet-shaped and dark-colored fruit bodies have earned it the common names devil's urn and the gray urn. The distribution of ''U. craterium'' includes eastern North America, Europe, and Asia. It produces bioactive compounds that can inhibit the growth of other fungi. The asexual (imperfect), or conidial stage of ''U. craterium'' is a plant pathogen known as ''Conoplea globosa'', which causes a canker disease of oak and several other hardwood tree species.

History and taxonomy

''Urnula craterium'' was first described in 1822 by American botanist Lewis David de Schweinitz as ''Peziza craterium'', based on a specimen found in North Carolina. The species first appeared in the scientific literature under its current name when Elias Magnus Fries described the new genus '' Urnula'' in 1849, and set ''Peziza craterium'' as the type species. In 1896, German mycologist Heinrich Rehm removed the species from ''Urnula'' – transferring it to the genus '' Geopyxis'' – and replaced the type species with ''Urnula terrestris'', a peripherally related species. This restructuring resulted in a taxomically untenable situation in which the genus ''Urnula'' consisted of a single species with ambiguous resemblance to the original species (described by Fries) upon which the genus was based. According to Elsie Kupfer, who had written Rehm to clarify the rationale for his decision:

''Urnula craterium'' was placed with its related species under ''Geopyxis'', because ''Geopyxis'' was established by Persoon before ''Urnula'' by Fries; and that in order to retain the genus ''Urnula'', under which Saccardo had placed ''Podophacidium terrestre'' of Niessl, he (Rehm) restricted the genus to this latter fungus.

As Kupfer explains, Rehm did not justify why he believed ''Urnula craterium'' should be allied to ''Geopyxis'', or why ''Podophacidium terrestre'' should be considered an ''Urnula''. Kupfer's macro- and microscopic analysis of tissues from these and related genera clearly showed the inconsistency in Rehm's taxonomical choices, and that ''Urnula craterium'' represented an entirely different genus not related to ''Geopyxis''; Fries's naming was restored.

The genus name means "little urn"; the specific epithet is derived from the Latin '' cratera'', referring to a type of bowl used in antiquity to mix wine with water. It is commonly known as the devil's urn and the gray urn.

Description

The fruit bodies begin from dense, black mycelium on the surface of oak branches in contact with the ground. Starting out as rolls of cylindrical tissue 1 or more centimeters long and 3–4 mm wide, they expand slowly over the winter, and grow rapidly in the spring when the weather becomes warmer.The goblet-shaped fruit body (technically an ascocarp) is in diameter and deep; initially it is closed, but opens as it matures, leaving a ragged or smooth inrolled margin around a round opening. The flesh of the ascocarp walls is tough and initially gelatinous, later becoming leathery. The exterior of the ascocarp is brownish black to black, with a velvety surface, while the interior spore-bearing surface, the hymenium, is brownish black in color, usually somewhat paler than the outside. The outer surface may be partially covered with small flakelike patches of tissue. When viewed with a magnifying glass, the "hairs" (fungal hyphae) making up the outer velvety surface are variable in length, and are thick-walled, blunt, and appear to wind from side to side (flexuous