Aspicilia cinerea
Thallus areolate to rimose on a shiny black hypothallus, areoles to 1 mm diam., very irregular, becoming warted or with knobbly papillae along margins in nutrient-rich environments, smooth, dull grey, becoming brown-tinged, grey-brown or rarely rust-coloured or green; prothallus black, visible both between the areoles and at the edge of the thallus. Isidia and soredia absent. Photobiont chlorococcoid algae.
Anamorph: conidiomata pycnidia, with filiform conidia 11-16 × ca 1 μm in size.
Teleomorph: ascomata apothecia, (0.2-)0.4-1.2(-2) mm diam., 1-2 per areole, at first immersed, later sometimes becoming sessile or slightly protruding. Thalline margin thick, not convoluted, white to pale grey, persistent. Disc slightly concave to flat, matt black. Interascal tissue composed of paraphyses, simple to sparingly branched, frequently anastomosed, short-celled and moniliform above, the apices cohering to form a well-defined epithecium. Asci clavate, thin outer coat K/I+ blue, wall and apical dome K/I–, (6-)8-spored. Ascospores 12-22 × 6-13 μm, broadly ellipsoidal, hyaline, aseptate, thin- and smooth-walled, without a gelatinous sheath or perispore.
Chemistry: thallus K+ red, Pd+ orange (norstictic acid).
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Assessed by Woods & Coppins (2012) as of Least Concern. The species is very widespread and frequently recorded, but many records may refer to other species in the A. cinerea aggregate.
Thallus features are very variable in this species, and it cannot reliably be distinguished from its close relatives Aspicilia epiglypta and A. intermutans in the field. Thalli can also resemble those of Circinaria caesiocinerea, but that species does not show a K reaction.
Aspicilia epiglypta and A. intermutans both have substantially larger ascospores than those of A. cinerea (20-28 µm versus 11-16 µm long). A. epiglypta is a relatively rare species that has long filiform conidia (15-28 µm long versus 11-16 µm in A. cinerea). In A. intermutans (commoner than A. cinerea s. str.) they measure 7-11 µm in length. Material is best collected in winter and spring to find conidia. As conidial length within a pycnidium is very variable, their maximum lengths need to be measured.
Very widely distributed in upland, mainly western parts of the British Isles.
On exposed siliceous rocks.