Bitter oyster

Appearance

The fungus normally exists unseen, in the form of a mass of threadlike vegetative cells called a mycelium, inhabiting rotting wood; only when suitable environmental conditions of temperature, moisture, and nutrient availability are achieved does the fungus produce the reproductive structures known as fruit bodies, or mushrooms.

The cap of the fruit body is kidney- or clamshell-shaped, convex to roughly flat, with dimensions of 1.2 to 3.2 cm by 1.2 to 2.5 cm. The edges of the caps are scalloped with small rounded teeth, and curved slightly inward.

The cap surface is dry, with a pattern of block-like areas similar to cracked dried mud; the surface is also covered with small fine hairs that give it a somewhat woolly consistency. It may have several concentric ridges or zones.

Fresh fruit bodies range in color from yellowish-orange to buff to cinnamon; when dried they may be various shades of tan, brown or clay. The faded colors of dried fruit bodies tend to revive when moistened.

On the underside of the cap, the gills are narrow and spaced closely together, often forked, buff-colored, and with numerous interconnecting cross-veins. Holding the cap in position is a stem that is 0.6 to 1.2 cm long by 0.3 to 0.8 cm thick, and has an off-center attachment to the cap, either at or near the cap side.

The dull-white stem is covered with minute silk-like fibers, and is narrower at the base where it attaches to the substrate. Fruit bodies do not have any distinctive odor. The flesh is thin and tough, and dark yellow-brown to cream-colored.

Naming

Species of "Crepidotus" having a similar shape can be distinguished by their brown spore print, compared with the white spore print of "P. stipticus". "Schizophyllum commune" has a densely hairy white to grayish cap and longitudinally split gill-folds on the underside.

The ruddy panus mushroom is larger, has a reddish-brown cap that fades to pinkish-tan, and shows lilac tinges when young, fresh, and moist. Some "Paxillus" species may have a similar appearance, but they have yellow-brown spore prints.

Distribution

"Panellus stipticus" is common in northern temperate regions of Europe, and has also been collected in Australia, New Zealand, Anatolia, Japan, and China. In North America, it is more common in the east than the west; the mushroom's northern range extends to Alaska, and it has been collected as far south as Costa Rica.

Habitat

"Panellus stipticus" is a saprobic species, and causes a white rot. This is a form of wood decay in which the wood assumes a bleached appearance and where lignin as well as cellulose and hemicellulose is broken down by enzymes secreted by the fungus.

Fruit bodies are usually found in tightly overlapping clusters on the sides of hardwood trees, on logs, stumps, and fallen branches. Although most commonly found on dead wood, it can also grow opportunistically in the wounds of living trees.

Predators

The fruit bodies are frequently attacked by slugs, which may be important agents in the dispersal of its spores. White-tailed deer are also known to consume the fungus.

Uses

"Panellus stipticus" is considered too small and bitter to be edible. Its taste has been described as acidic, acrid, or astringent.