Arthonia radiata (aka “Asterisk Lichen”)

Identification Characteristics

Description: Thallus thin, pale to white, in small patches on trees.  Ascomata black, elongate & branching, up to 1.5 mm long & 0.1 – 0.2 mm broad, forming star-like clusters similar to those of a tiny script lichen.

Spores: 15 – 21 x 4.5 – 7 um, 4-celled with all the cells approximately the same size.

Chemistry: No lichen substances.

Substrate: On bark of many kinds, especially the smooth bark of hardwoods.

Habitat: Typically in forests.

Lookalikes: In the east, Arthonia radiata is often accompanied by A. patellulata, a common species with a thidden thallus that creates pale patches on the bark of poplars & other hardwoods.  Its fruiting bodies are black & round, resembling biatorine apothecia without a margin, & the spores are 2-celled.

Bibliography: Lichens of North America, by Brodo, Sharnoff, & Sharnoff

Database Entry:  Distance Everheart 12-26-13