Arthonia cinnabarina (aka “Bloody Comma Lichen”)
Description: Thallus largely immersed in the bark, forming a gray to pinkish patch often bordered by a thin, brown prothallus. Ascomata irregularly ellipsoid, rarely branched, 0.3 – 1 x 0.2 – 0.5 mm, brown, usually with dark red or red-orange pruina on the edges; surface of “disk” white or red pruinose, or naked.
Spores: Mostly 5 – 6 celled, strongly tapered, with the end cell noticeably larger than others, 18 – 28 x 7 – 10 um.
Chemistry: Red pruina is K+ red-purple (several anthraquinones).
Substrate: On bark.
Habitat: Usually in shaded woods.
Lookalikes: The spores & red, K+ purple pruina on the fruiting bodies are usually enough to distinguish this striking lichen.
Bibliography: Lichens of North America, by Brodo, Sharnoff, & Sharnoff
Database Entry: Distance Everheart 12-26-13