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Rinodina exigua (Ach.) Gray, Nat. Arr. Brit. Pl. (London) 1: 450 (1821) Description: Thallus thin or rarely evanescent, pale to dark grey, continuous or cracked, flat or more rarely granular, effuse; prothallus inconspicuous. Apothecia 0·3–0·6 mm diam., sessile, frequent and often contiguous; thalline exciple c. 0·05 mm wide, concolorous with thallus, entire and persistent; disc black, rarely dark brown; epithecium dark brown; hymenium 70–110 µm tall; hypothecium 45–115 µm tall. Asci 45–65 × 13–20 µm. Ascospores 11·5–23 × 5·5–9·5 µm, Physcia-type. Atranorin may be present in low concentration.
Habitat: On the rough bark of old tree trunks; fairly common.
Notes: R. sophodes (26) has a brownish olive thallus with ± immersed apothecia and is more characteristic of twigs, especially Fraxinus. Some records on enriched, dust-impregnated bark or wood may refer to R. gennarii (11).
Distribution: Other: C. & S. England, C. Scotland, Ireland. Widespread in temperate regions of N. & S. Hemispheres.
Vouchers:
Descriptions, Lists & Icons:
L: Checklist of British lichen-forming, lichenicolous and allied fungi, in Hawksworth, D.L.; James, P.W.; Coppins, B.J., Lichenologist 12: 1-115 (1980), p. 89
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