Arthrorhaphis (aka “Dot Lichens”)

Description: Thallus consisting of bright yellow or gray granules, convex areoles, or squamules, or growing within the tissues of a host lichen; medulla sometimes containing masses of colorless, irregular crystals of calcium oxalate (insoluable in K, soluble in strong acid).  Ascomata pitch black, flat to slightly convex, resembling apothecia, without a distinct margin; exciple poorly developed; paraphyses branched & anastomosing; asci K/I-, barely thickened at the tip.

Spores: Colorless, needle-shaped, 9 – 12 celled, 8 per ascus.

Photobiont: Green (unicellular).

Chemistry: PD-, K-, KC-, C-, UV+ orange (rhizocarptic acid).

Substrate: On disturbed soil such as roadsides & frost boils.  Several species in this genus are parasite lichens.

Range: Boreal to Arctic.

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