Hypotrachyna lividescens (Kurok.) Hale

Phytologia, 28, 4: 341, 1974. Basionym: Parmelia lividescens Kurok. - in Hale & Kurokawa, Contr. U.S. Natnl. Herb., 36: 181, 1964
Description: Thallus foliose, heteromerous, dorsiventral, closely adnate, forming more or less regular, 3-8(-10) cm wide rosettes, sorediate. Lobes 1-3(-4) mm wide, subdichotomously branched with rounded axils and truncate to subrotund tips, linear-elongate, more or less crenulate, flat to slightly convex, separate to contiguous; upper surface very pale ash-grey (sometimes almost whitish), emaculate, smooth to somewhat rugulose, dull but shiny in younger lobes, irregularly cracked in older lobes, with laminal or subterminal, orbicular to subcapitiform, sometimes confluent soralia bearing whitish to greenish, farinose soredia; lower surface black in central parts, brown at margins, usually shiny, with sparse to moderately dense, short, black, more or less shiny, dichotomously branched rhizines which sometimes project beyond lobe margins. Upper cortex of tightly packed, anticlinally oriented hyphae, with a pored epicortex, the cell walls with isolichenan; medulla white; algal layer continuous; lower cortex brown, of anticlinally oriented hyphae. Apothecia rare, lecanorine, laminal, substipitate, 2-5(-8) mm across, with a dark brown disc and a sorediate, crenulate thalline margin. Epithecium brownish; hymenium and hypothecium colourless. Asci 8-spored, clavate, Lecanora-type. Ascospores 1-celled, hyaline, broadly ellipsoid, 9-13 x 5-8 µm. Photobiont chlorococcoid. Spot tests: upper cortex K+ yellow, C-, KC-, P+ yellow, UV-; medulla K-, C+ red turning orange-red, KC+ orange-red, P-. Chemistry: upper cortex with atranorin and chloroatranorin; medulla with olivetoric acid (major), anziaic acid (minor) and traces of other substances.
Note: a mainly epiphytic species known from South Africa, Australia and Western Europe, in France extending from the Atlantic coasts to Provence; to be looked for in Tyrrhenian Italy.
Growth form: Crustose
Substrata: bark
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)

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