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Placynthium (Ach.) Gray (1821)

Data Set Maintenance: Data set standard item. Data set author(s): Rambold G. Data set reviewer(s): Scholz P. (02-05-16); revised; to be published after submission.

Nomenclature: Current taxonomic status: accepted. Taxonomic rank: genus. Number of known taxa within this rank: 25. Placynthium. Placynthiaceae Dahl (1950); Peltigerineae; Lecanorales.

Type Information: Type: Placynthium nigrum (Ach.) Gray.

Taxonomic Literature: Clauzade G. & Roux C., Bull. Soc. Bot. Centre-Ouest N.S. - Numero
Special 7: 1-893 [609-611] (1985); Galloway D.J., Flora of New
Zealand Lichens: i-lxxiii, 1-662 [409], Wellington (1985); Gilbert
O.L. & James P.W. in: Purvis O.W. et al. (eds), The Lichen Flora
of Great Britain and Ireland, London (1992); Henssen A., Can. J. Bot.
41: 1687-1724 (1963); Keuck G., Biblioth. Lichenol. 6: 1-175 (1977); Schultz M. in: Nash T.H. III et al. (eds) Lichen Flora of the Greater Sonoran Desert Region vol. 1, 397-399, Tempe (2002).

Biogeography: Checklist records: Austria, Germany, Great Britain, Italy, New Zealand, Sonoran Desert, Sweden and Norway, Thailand, and United States and Canada (continental).

Ecology: Biotroph; lichenized; terricolous or rarely corticolous; substrate non-calciferous or calciferous.

Lichen Photobionts: Primary photobiont present; cyanobacterial. Primary photobiont taxonomy: Dichothrix or Scytonema (A. Beck 22-05-97); Rivulariaceae or Scytonemataceae; Nostocales, Cyanobacteria, Prokaryota. Secondary photobiont absent.

Thallus: Crustose (subsquamulose) or small foliose, not subdivided parts, squamulose, placodioid, granular, or areolate (primarily areolate), small lobed. Thallus Outline: Soon disappearing or persistent. Upper Surface: Black, grey, green, brown, olive, or brownish yellow; special structures absent or present:; not pseudocyphellate; eciliate; without hairs; not isidate or isidiate; not sorediate; not cephalodiate; not lobulate or lobulate; without granules granules, without thalloconidia thalloconidia. Lower Surface: Attached by the whole lower surface or attached by holdfasts; special structures absent; not pseudocyphellate; not cyphellate; not rhizinate; without thalloconidia thalloconidia; not cavernulate; not tomentose.

Reproduction Strategy: Only known as sterile, asexually reproducing form or with sexual (and possible asexual) stages. Ascocarps: Apothecioid, orbicular, forming all across the thallus surface, not emerging, becoming adnate, soon sessile, or stipitate. Margin: Distinct or prominent; external filaments absent. Exciple: Black, grey, or brown. Periphyses: Absent. Epithecium: Apical cells green or brown. Interascal Hyphae: Present, scarcely branched, not or scarcely anastomosed. Hypothecium: Brown or white.

Asci: Tholus thickened, amyloid, with amyloid tube; dehiscence lecanoralean.

Ascospores: c. 4 or c. 8 per ascus, broadly ellipsoid, ellipsoid, fusiform, or oblong, 7-53 µm long, 3.5-9 µm wide, obtuse; septa absent or present; transversally septate, 1-7-transversally septate; wall thin, not thickened at the septum, hyaline, in Lugol's Solution negative, wall not ornamented.

Conidiomata: Absent resp. not observed or present; pycnidial; immersed, formed all accross the thallus surface.

Conidia: Ellipsoid, bifusiform, or bacilliform.

Secondary Metabolites: Not detected.

(report generated 04.Okt.2007)

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