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Images of British Lichens

Opegrapha rufescens Pers.

Thallus thin, grey to olive- or red-brown; fruitbodies shortly elongated, curved or sometimes stellate, lirellate apothecia up to 1mm in length, often crowded, opening to expose the discs, with thin, true margins and sometimes with outer, thin, raised, whitish, 'pseudothalline' margins. Part of a difficult genus commonly requiring microscopic examination of the spores for accurate identification, ascospores 3-septate, narrow, straight or curved, (15-)17-27 × 3-5 µm (dimensions from Pentecost & James, in Smith et al., 2009). Widespread but local on sheltered, smooth, nutrient-rich bark.

Refs: Smith et al. (2009), 643; Purvis et al. (1992), 412; Dobson (2005), 291 (photo); Dobson (2011), 294 (photo); van Herk & Aptroot (2004, 2013), 272-3 (photo); Frahm et al. (2010), 69 (photo); Wirth, Hauck & Schulz (2013), 2: 790, 793 (photo); Holien & Tønsberg (2008), 198 (photo); Puntillo (1996), plate 27 (photo).

Opegrapha rufescens
On Ash (Fraxinus excelsior) in old woodland, Ashton Court, Bristol, February 2013 (BLS meeting)

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uploaded February 2014