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Physcia dimidiata (Arnold) Nyl.

Data Set Maintenance: Data set compiled (from Sonoran Lichen Flora Vol.1). Data set author(s): Bungartz F. (02-02-07). Data set to be published after submission; February 2002.

Nomenclature: Current taxonomic status: accepted. Taxonomic rank: species. Currently accepted name Physcia dimidiata (Arnold) Nyl. Physcia. Physciaceae Zahlbr. (1898); Lecanorineae; Lecanorales.

Type Information: Basionym: Parmelia pulverulentula var. dimidiata Arnold. Type: Physcia dimidiata (Arnold) Nyl.

Biogeography: Colline and submontane. Continent: Europe, Northern America, and Southern America. Checklist records: Germany, Mexico, and Sonoran Desert.

Ecology: Biotroph; lichenized; lignicolous, corticolous, or saxicolous (in Sonoran Region mainly on N-exposed rock); episubstratic; growing sun-exposed or partially shaded; under conditions which are dry or moist.

Thallus: Foliose, subdivided into main parts, lobed; lobes ascending (at the tips); more or less imbricate; separate thallus parts up to (3) mm wide. Thallus Size and Differentiation: Up to (3) cm in diameter; apex rounded (not rounded but crenulate). Thallus Outline: Irregular or sometimes orbicular; margin lobulate; soon disappearing. Upper Surface: Grey (to cream), grey-brown, or pale grey, smooth; immaculate; pruina whitish; eciliate; without hairs; not isidate; sorediate; soralia grey or grey-brown, peripheral, soredia coarse; not blastidiate; not schizidiate; not lobulate. Lower Surface: Present, white or pale brown; attached by holdfasts (true rhizines); rhizinate; rhizines pale grey or brown, without projections, not branched (rhizines simple to sparsely furcate), sparsely furcate; not sorediate; not tomentose.

Upper Cortex: Present; outer cortical layer paraplectenchymatous; inner cortical layer prosoplectenchymatous. Medulla: White. Lower Cortex: Present.

Ascocarps: Apothecioid, orbicular, soon sessile or substipitate, up to 2 mm in diam.. Margin: Lecanorine, persistent, distinct. Disk: Plane; pruinose, pruina abundant, white. Epithecium: With epithecium; apical cells subulate (clavate with dark brown cap). Hymenium: White; not inspers. Interascal Hyphae: Scarcely branched (paraphyses simple or forked above). Subhymenium: White. Hypothecium: White; not inspers.

Asci: Cylindrical; dehiscence lecanoralean (Lecanora-Type).

Ascospores: Physcia-type, c. 8 per ascus, ellipsoid, 17-23 µm long, 8-12 µm wide; septa present; transversally septate; 1-transversally septate; wall thickened at the septum, becoming pigmented, dark brown (at maturity) or middle brown.

Secondary Metabolites: Present; only in the upper part of the cortex, atranorin.

Spot Tests: Present reactions. Upper surface: K + deep yellow, C –, KC –, PD + yellow; cortex: KC + deep yellow, medulla: K – C –, KC –, PD – soredia: K – KC –.

(report generated 13.Nov.2007)

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