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All Fungi
Arthonia didyma
Nomenclature
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Family: ArthoniaceaeGenus: Arthonia
SUMMARY
Thallus immersed, effuse, wide-spreading or in tiny patches (especially around lenticels and scars), inconspicuous, pale fawn or olive-grey, sometimes pale pink when fresh. Soredia and isidia absent. Photobiont Trentepohlia.
Anamorph: conidiomata pycnidia, 40-60 μm diam., rare, immersed, the wall red-brown, K+ olive-grey. Conidia 3.5-4 × ca 0.7 μm, bacilliform.
Teleomorph: ascomata arthonioid apothecia, 60-600 × 60-300 µm, irregular in form but often rounded to shortly linear, flat, dark brown to brown-black, matt, not pruinose; in section 45-70 (-100) μm tall. Epithecium red-brown or indistinct. Hymenium 33-50 μm tall, hyaline or pale orange-red-brown in parts. Hypothecium 5-30 μm tall, red-brown; red-brown pigment K+ grey or olive, but epithecium, hymenium and sometimes hypothecium with additional orange-red, K+ purple-violet pigment. Interascal tissue of paraphysoids 0.5-1 (-1.5) μm diam., rather scanty, or (especially in epithecium) brown-walled and to 2.5 μm diam., a few with apical caps. Ascospores (12-) 14-17 × 4.7-7 μm, ovoid, 1-septate, constricted at the septum, thick-walled, at first hyaline and smooth, becoming brown and warted, without an epispore or gelatinous sheath or appendages.
Chemistry: no lichen products or anthraquinone(s) detected by TLC.