devil's urn

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 3–4 cm (1+1⁄4–1+1⁄2 in) in diameter and 4–6 cm (1+1⁄2–2+1⁄4 in) 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). The ascocarp is connected to a stalk that is typically 3–4 cm (1+1⁄4–1+1⁄2 in) long by 0.4–0.8 cm (1⁄8–3⁄8 in) thick, with black mycelia at its base.

Microscopic features. The spores are ellipsoid or sausage-shaped (allantoid), smooth, and thin-walled. …

Urnula craterium grows singly or clustered together, usually attached to sticks and branches (especially oak) that are partially buried in the ground. The teleomorph state is saprobic, and decomposes hardwood; the anamorph state is parasitic, and causes a canker of various hardwoods, including oaks, hickories, basswood and beech. It is often found in deciduous forests, although it is sometimes inconspicuous due to its dark color, and because it may be partially covered with leaf litter. One of the first fleshy fungi to appear from March to May, U. craterium has been dubbed a "harbinger of spring", and is sometimes encountered under melting snow. The distribution of U. craterium includes eastern North America, Europe (including the Czech Republic, Finland, and Spain), Japan, and China. It is red-listed as critically endangered in the Czech Republic.

This species is often listed in field guides as inedible, or not recommended for consumption due to its tough texture. Michael Kuo, in his 2007 book on edible mushrooms, lists the taste as "mediocre", and comments "the devil's urn is not as bad as I thought it was going to be. It's not good, mind you, but it would be possible to eat it with a forced smile if your Aunt Wanda served it to you."

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.