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