Enchylium polycarpon
Thallus 2-6 cm diam., forming rosette-like cushions, foliose, deeply lobed, rather thick. Lobes 1-2.5 mm wide, numerous, crowded, ± radiating, ± flattened, contiguous, often ascending at the centre of the thallus, often channelled towards the apices with raised margins, swollen, somewhat contorted. Upper surface dark olive-green to black, without isidia.
Anamorph: no information available.
Teleomorph: ascomata apothecia, numerous, terminal and on raised margins, ± elevated, crowded and frequently covering the thallus except the outermost parts of lobes, mostly appearing stalked. Disc 0.5-1.5 mm diam., flat to convex, with a rather thin, smooth thalline exciple. Ascospores 18-28 × 6.5-8.5 μm, fusiform with acute apices, 1- to (2-) 3-septate.
Assessed by Woods & Coppins (2012) as of Least Concern, but listed as Nationally Scarce due to the paucity of records. It may be under-reported.
Enchylium corresponds to the Collema tenax group as traditionally circumscribed. E. polycarpon is recognized by its thick, often ascending, lobes with terminal apothecia. Lathagrium (Collema) cristatum has canaliculate lobes and submuriform spores.
Locally distributed in most areas of the British Isles with suitable rock types.
On hard, moist, exposed limestone, often associated with Enchylium (Collema) multipartitum.