Pebbled Pixie Cup

Description

Pebbled Pixie Cup is a common, cosmopolitan lichen. It occurs worldwide on every continent including Antarctica. In the United States it is common in the east and in the west, but it is mostly absent from the deep south, the desert southwest, the Great Plains, and the Great Basin. It grows under full sun or partial shade, on soil, especially on acidic soil and thin soil over rocks, and it rarely grows on wood.

Pebbled Pixie Cup produces two types of vegetative growth (thallus). The primary thallus is a leaf-like scale (squamule) that lies on the soil. The squamules are numerous but often small and inconspicuous, 1⁄16″ to 3⁄16″ (2 to 5 mm) long, 1⁄32″ to ⅛″ (1 to 3 mm) wide, and very thin, less than 1⁄64″ (0.4 mm) thick. The margins may be irregularly lobed, toothed, cut (incised), or smooth (entire). The lobes are mostly ascending, and they never form a rosette-like crust. The squamules are persistent, remaining as the secondary thallus matures.

The secondary thallus is a vertical, unbranched, greenish gray to brown stalk (podetium) that is ⅛″ to ¾″ (3 to 20 mm) tall and rises from the primary thallus. The podetium broadens gradually at the tip into a 5⁄16″ to ½″ (8 to 12 mm) in diameter cup. A key characteristic identifying this species is the podetium widening gradually from the base to the cup without a distinct, narrow stalk.

The cup is undivided and the margins are unlobed. The layer of protective tissue (cortex) may be complete up to the cup, just at the base, or entirely missing. When present, the cortex is warty, and it breaks up into granules or gives rise to tiny, asexual, reproductive structures. When these are formed in the cup, they may appear like appressed squamules, a feature characteristic even in young specimens.

Egg-shaped, reproductive, flask-like structures (pycnidia) are very common on the margins. Disk-shaped reproductive structures (apothecia) on the margins of the cup are also common. They are up to 5⁄16″ (8 mm) wide, on stalks about ⅛″ (3 mm) long, and reddish brown to a darker color.

Pebbled Pixie Cup contains fumarprotocetraric acid, which causes a red reaction during standard lichen spot testing (the P+ red test).

Similar Species

Ecology

Substrate

Ground

Growth Form

Fruticose

Habitat

Hosts