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Images of British Lichens

Opegrapha sorediifera P.James

Thallus thin, greyish to brown, bearing small soralia that may coalesce, soredia powdery, pale orange-yellow; fruitbodies (when present), tiny, shortly elongated, lirellate apothecia up to 0.6(-1.3)mm in length, discs remaining slit-like. The soredia are diagnostic, but part of a difficult genus commonly requiring microscopic examination of the spores for accurate identification, ascospores 10-14-septate, needle-like, 30-40(-58) × 4-5 µm (dimensions from Pentecost & James, in Smith et al., 2009). Widespread but local on sheltered bark in damp woodland.

Refs: Smith et al. (2009), 644; Purvis et al. (1992), 413; Dobson (2005), 291-2 (photo); Dobson (2011), 294 (photo); Arup et al. (1997), 225 (photo); Thor & Arvidsson (1999), 293 (photo).

Opegrapha sorediifera
Opegrapha sorediifera, close view
On Larch (Larix) twig, partly obscured by free-living algae, Ballygrant, Islay, May 2011 (BLS meeting)

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uploaded February 2014