Cyphellostereum georgianum

The lichen produces a crustose‑filamentous thallus: a thin, firmly attached crust made of countless intertwined cyanobacterial‑fungal threads. At its base the thallus forms a continuous dark‑green carpet; above this are irregular, slightly raised patches where the threads are packed more densely, giving a yellow‑green tinge.^[2]

Under the microscope each thread (called a fibril) consists of a chain of cyanobacterial cells 7–12.5 μm wide sheathed by branched fungal hyphae. Occasional pale‑yellow heterocytes—specialised nitrogen‑fixing cells—punctuate the filaments. Clamp connections on the fungal hyphae confirm its basidiomycete identity.^[2]

Reproduction occurs on the underside of the lichen where tiny, white, crust‑like pads (the hymenophores) develop. These corticioid basidiocarps can reach 14 mm long but remain only about 2 mm across. In section the fertile layer is up to 100 μm thick and built of 2–4 μm hyphae; immature club‑shaped structures (basidioles) measure 3–4 × 12–18 μm. Mature basidia and basidiospores have not yet been observed.^[2]

Microscopically, C. georgianum builds a dark‑green crust of densely tangled fibrils that rise into thick, mound‑like patches, whereas its sister species C. jamesianum spreads as a much looser layer of individual to only slightly interwoven fibrils. C. jamesianum is also thinner and more bluish, with clearly separated, sometimes yellow‑tinged fibrils, and it lacks the elevated patches that give C. georgianum its mottled texture.^[2]

As of its original publication, Cyphellostereum georgianum is known only from the type locality in Harper Lake Park, Georgia, where it grows on the bark of live hardwoods such as oaks within a low‑lying pine–oak woodland. The surrounding canopy is dominated by Pinus taeda with a mixed mid‑storey of Quercus hemisphaerica, Q. geminata, Ilex opaca and other broad‑leaved species; shrubs include saw palmetto and various blueberries. The lichen overgrows bark and adjacent bryophyte mats in humid, shaded microhabitats but has not been recorded outside this site.^[2]