Hairy Rubber Cup

Hairy Rubber Cup (Galiella rufa) is a distinctive ascomycete of the Sarcosomataceae, the family of rubbery and gel-filled cup fungi. Its fruit body feels quite unlike an ordinary cup fungus: firm, elastic and rubbery, springing back when squeezed and drying to a hard black knot.

The outer surface is dark brown to nearly black and covered in a dense pelt of short stiff hairs, while the fertile disc inside is smooth and a warm reddish to purplish brown. Young specimens are almost closed, opening by a small round mouth that widens as the cup expands, which gives the fungus a top-shaped or goblet outline.

It is a familiar summer fungus of eastern North American hardwood forests, often fruiting in rows along a single fallen branch.

Fruiting body

Top-shaped to goblet-shaped, 1–4 cm across and about as tall, narrowed below into a short thick stalk-like base. It begins closed and nearly spherical, then opens by a small pore that expands into a broad disc.

Disc and outer surface

The fertile disc is smooth, reddish brown, chestnut or purplish brown, often becoming slightly wrinkled with age. The outer surface and the rim are blackish brown, roughened and densely coated with short stiff bristly hairs; the rim frequently retains an inrolled, fringed appearance.

Flesh and spore print

The flesh is the giveaway: thick, gelatinous-rubbery, elastic and tough, pale brown within, not brittle like a Peziza. Dried fruit bodies shrink to hard, black, horny lumps. The spore print is whitish.

Galiella rufa fruits on dead hardwood — fallen sticks, branches and small logs, often partly buried in leaf litter — in moist deciduous and mixed forest. Oak, hickory and other hardwoods are typical hosts, and it favours shaded slopes, ravines and stream sides.

Fruiting occurs in summer and early autumn, later than most spring cups. It is common through eastern North America and is also known from parts of Asia.

This is a wood-decay saprophyte that colonises small-diameter hardwood debris, contributing to the breakdown of branches on the forest floor. The rubbery flesh helps the fruit bodies survive dry spells, rehydrating and continuing to release spores when rain returns.

Because several fruit bodies commonly arise from the same branch, finding one usually means finding a line of them along the buried wood.

Bulgaria inquinans, the black bulgar, is similarly rubbery but has a black, shiny fertile disc rather than a reddish-brown one, a brown scurfy rather than bristly outer surface, a dark spore deposit that blackens the fingers, and it grows in clusters on fallen oak bark. Sarcosoma globosum is far larger, almost spherical, filled with watery gel, and fruits under conifers in spring. Wolfina aurantiopsis has a paler orange to ochre disc and a lighter hairy exterior. Ordinary Peziza cups are thin and brittle, tearing rather than flexing.

Rubbery elastic flesh plus a reddish-brown disc in a blackish bristly cup identifies Galiella rufa.