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Placidium A. Massal. (1855)

Data Set Maintenance: Data set standard item. Data set author(s): Rambold G. Data set reviewer(s): Keller C. (98-05-20) and Scholz P. (02-05-16); revised; to be published after submission.

Nomenclature: Current taxonomic status: accepted or basionymous. Taxonomic rank: genus. Number of known taxa within this rank: 32. Placidium. Verrucariaceae Zenker (1827); Verrucariales.

Type Information: Type: Placidium michelii A. Massal.

Taxonomic Literature: Taxonomic notes: Cells of upper cortex large; involucrellum not developed; asci
cylindrical; pycnidia of Xanthoria-type.
Breuss O., Linzer Biol. Beitr. 20: 829-845 (1988) - sub Catapyrenium;
Breuss O., Stapfia 23: 1-174 (1990) - sub Catapyrenium; Breuss O.,
Linzer Biol. Beitr. 22: 69-80 (1990) - sub Catapyrenium; Breuss O.,
Linzer Biol. Beitr. 24: 813-815 (1992) - sub Catapyrenium; Breuss O.,
Pl. Syst. Evol. 185: 17-33 (1993) - sub Catapyrenium; Breuss O.,
Linzer Biol. Beitr. 25: 339-346 (1993) - sub Catapyrenium; Breuss O.
in: Daniels F.J.A., Schulz M. & Peine J. (eds): Flechten Follmann: 175-178, Cologne (1995) - sub Catapyrenium; Breuss O., Linzer Biol. Beitr. 98B Suppl.: 35-53 (1996); Breuss O. in: Nash T.H. III et al. (eds) Lichen Flora of the Greater Sonoran Desert Region vol. 1, 384-393, Tempe (2002); Breuss O. & Etayo J., Plant Syst. Evol. 181: 255-260 (1992) - sub Catapyrenium; Breuss O. & Hansen E.S., Plant Syst. Evol. 159: 95-105 (1988) - sub Catapyrenium; Breuss O. & McCune B., Bryologist 97: 365-370 (1994) - sub Catapyrenium; Harada H., Nat. Hist. Res. 2: 113-152 (1993) - sub Dermatocarpella; Thomson J.W., Bryologist 90: 27-
39(1987) - sub Catapyrenium.

Biogeography: Checklist records: Germany and Sonoran Desert.

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

Lichen Photobionts: Primary photobiont present; chlorococcal. Primary photobiont taxonomy: Myrmecia. Secondary photobiont absent.

Thallus: Crustose, not subdivided parts, squamulose. Thallus Outline: Persistent. Upper Surface: Brown; special structures absent or present:; not pseudocyphellate; eciliate; without hairs or hairy; not isidate; not sorediate; not cephalodiate; not lobulate; without granules granules, without thalloconidia thalloconidia. Lower Surface: Attached by holdfasts; special structures present:; not pseudocyphellate; not cyphellate; not rhizinate or 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: Perithecioid, orbicular, forming all across the thallus surface, not emerging. Wall: Not carbonized, not fused. Margin: Indistinct; external filaments absent. Exciple: Brown, white, or brownish yellow. Periphyses: Present. Hymenium: Iodine reaction: Lugol’s negative or Lugol’s positive, hemiamyloid. Interascal Hyphae: Absent. Hypothecium: White or brownish yellow.

Asci: Ocular chamber indistinct; dehiscence verrucarial; exoascus not amyloid, not hemiamyloid.

Ascospores: c. 8 per ascus, broadly ellipsoid or ellipsoid, 11-24 µm long, 5-11.5 µm wide, obtuse; septa absent; 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 or along the thallus periphery.

Conidia: Bacilliform.

Secondary Metabolites: Not detected.

(report generated 04.Okt.2007)

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