Opegrapha rupestris
Description : Thallus to 0.2 mm thick, in isolated to confluent, round to irregular patches, 0.5–2 cm diam., margins effuse to delicately crenate, sometimes delimited by a thin, wavy, black prothalline line, especially when forming interlocking mosaics. Surface white or grey-white, occasionally somewhat brownish centrally, tartareous, continuous to minutely cracked, slightly roughened–scurfy. Apothecia coal-black, very variable, 0.5–1(–1.5) mm long, 0.1–0.2 mm wide, 40–120 μm tall, sessile to somewhat immersed, scattered or contiguous, simple, straight or curved, to branched and clustered–stellate; disc a slit, sometimes slightly exposed with age. Hymenium 80–100 μm tall; epithecium brown, K+ greenish. Ascospores ellipsoidal, 3-septate, 16–20(–24) × 4–5(–6.5) μm. Pycnidia frequent, scattered, black, to 0.3 mm diam. Conidia straight, bacillar 4–7 × 0.5–1.5 μm.
Chemistry : TLC−, all reactions negative.
S: Marlborough (Kaikoura Peninsula). On coastal limestone rocks, associating with Caloplaca spp., Lecanora crenulata and Porina corrugata. Known also from Europe, Scandinavia, and North America (Nimis 1993; Santesson 1993; Esslinger & Egan 1995; Diederich & Sérusiaux 2000; Scholz 2000; Brodo et al. 2001; Hafellner & Türk 2001; Llimona & Hladun 2001; Nimis & Martellos 2003; Santesson et al. 2004).
Cosmopolitan
Illustrations : Dobson (2000: 251 – as Opegrapha saxatilis; 2005: 295)
Opegrapha rupestris is characterised by: the saxicolous habit (limestone rocks); the tartareous, white or grey-white thallus; scattered to contiguous, sessile to subimmersed, coal-black lirellae; and 3-septate ascospores, 16–20(–24) × 4–5(–6.5) μm.
