Vinegar Cup

Helvella acetabulum has a deeply cup-shaped fruit body (technically an apothecium) that is up to 8 centimetres (3 inches) in diameter, and 4 cm (1+1⁄2 in) deep. The cream-colored stem is typically 1 to 6 cm (1⁄2 to 2+1⁄2 in) tall by 1 to 3 cm (1⁄2 to 1+1⁄4 in) thick, with ribs extending almost to the top of the fruit body. The fruit body's exterior surface is cream-colored towards the stem and may feel subtly grainy near the margin. The inner spore-bearing surface, the hymenium, is brownish and possibly smooth or slightly wavy. The mushroom's odor and taste are not distinctive. The spores are smooth, elliptical, translucent (hyaline), and contain a single central oil droplet; they have dimensions of 18–20 by 12–14 μm. The spore-bearing cells, the asci, are 350–400 by 15–20 μm, are operculate—meaning they have an apical "lid" that releases the spores. The tips of the asci are inamyloid, so they do not adsorb iodine when stained with Melzer's reagent. The paraphyses are club-shaped, and have a pale brown color, with tips that are up to 10 μm thick.

Similar species. Helvella queletii has a roughly similar form and appearance, but the ribbing in that species does not extend up the margin as does H. acetabulum. H. griseoalba has ribs that extend halfway up the sides of the fruit body, but the color of the cup is pale to dark gray rather than cream. The ribs of H. …

This fungus is widespread in North America and Europe. In North America, the distribution extends north to Alberta, Canada. In Mexico, it has been collected from State of Mexico, Guanajuato, Guerrero, and Tlaxcala. It is also found in Israel, Jordan, Turkey, Iran China (Xinjiang) and Japan. The fruit bodies grows solitary, scattered, or clustered together on soil in both coniferous and deciduous woods, typically in spring and summer. A preference for growing in association with coast live oak (Quercus agrifolia) has been noted for Californian populations.

The specific epithet acetabulum means "little vinegar cup", and was the Latin word for a small vessel used for storing vinegar (see acetabulum). Common names include the "cabbage leaf Helvella", the "vinegar cup", the "ribbed-stalk cup", and the "brown ribbed elfin cup".