Collema furfuraceum  

Thallus 3-6(-10) cm diam., foliose, membrane-like, thin, closely appressed, conspicuously lobed. Lobes 5-10 mm wide, few, rounded or extended, ± overlapping. Upper surface dark olive-green to black, paler and ± transparent when moist, markedly ridged. Lobe ridges radiating, in young parts of thallus short, sometimes ± rounded, becoming long, narrow and flexuous, 0.1-0.3 mm wide, ca 1.5 mm tall, simple or branched. Isidia present on ridges, abundant, terete, cylindrical, to 0.3 mm long, simple or branched and coralloid when old.
Anamorph: no information available.
Teleomorph: ascomata apothecia, very rare. Disc 0.5-1.5 mm diam., flat, with a densely isidiate thalline exciple. Ascospores 40-80 × 3-6.5 μm, fusiform to acicular, often curved, 4- to 5-septate.