Sclerophyton circumscriptum (Taylor) Zahlbr.

Data Set Maintenance: Data set authentic and standard item. Data set author(s): Egea J. M. & Torrente P. (00.03.23). Data set not to be published after submission.

Nomenclature: Current taxonomic status: accepted. Taxonomic rank: species. Sclerophyton. Genus of unknown placement (incertae sedis) (Roccellaceae Chevall 1826); Arthoniales.

Taxonomic Literature: Egea J.M. & Torrente P., The Briologist 98: 207-217 (1995); Redinger K., Repertorium Specierum Novarum Regni Vegetabilis 43: 49-77 (1938).

Biogeography: Continent: Africa (Northern), Europe, and Northern America. Checklist records: Sonoran Desert.

Ecology: Biotroph; lichenized, episubstratic; growing partially shaded or fully shaded, under conditions which are moist; substrate non-calciferous.

Lichen Photobionts: Primary photobiont present, trentepohlioid.

Thallus: Crustose, not subdivided parts, rimose; separate thallus parts thick. Thallus Outline: Often persistent. Upper Surface: Grey, white, or brownish yellow, smooth, slightly pulverulaceous; special structures absent; epruinose; without hairs; not sorediate, soralia isolated, not confluent with other soralia.

Reproduction Strategy: With sexual (and possible asexual) stages. Ascocarps: Perithecioid, orbicular or irregular, forming independently from the host thallus or mycelium, not emerging, abundant, .3 mm in diam.. Margin: Indistinct; external filaments absent. Disk: Plane, black, pruinose, pruina white. Exciple: Not carbonized, brownish red (above) or pale brown. Amphithecium (thalline excipulum): Photobiont absent. Amphithecial Cortex: Absent. Epithecium: Without epithecium; apical cells not swollen or slightly swollen. Hymenium: 100-150 µm high, white, iodine reaction: Lugol’s positive, hemiamyloid. Interascal Hyphae: Present, distinctly branched, distinctly anastomosed; cells 1 µm wide. Hypothecium: Pale brown, pigment not homogenously distributed.

Asci: Narrowly clavate, indistinctly stipitate, 70-95 µm long, 15-19 µm wide; tholus thickened, amyloid, hemiamyloid, in Lugol's Solution + dark blue, with amyloid tube; dehiscence bitunicate; endoascus hemiamyloid throughout.

Ascospores: c. 8 per ascus, oblong-obtuse or clavate, (17)-19-26 µm long, 5-7 µm wide, obtuse; septa present, 4-6-(7)-transversally septate; lumina apically enlarged, constricted at the centre; wall thick, distinctly differentiated into primary and secondary wall, laterally constricted where the septum meets the spore wall, dark brown, not ornamented, distinctly halonate, i.e., with a thick mucilaginous sheath.

Conidia: Filiform.

Secondary Metabolites: Present, 2'-O-demethylpsoromic acid or psoromic acid.

Spot Tests: Present reactions. Upper surface: K – (negative) or + deep yellow, KC –, PD + orange.

(report generated 04.Okt.2007)