Catolechia wahlenbergii  

Thallus ± orbicular, squamulose (squamules 0.1-0.5 mm diam.) to ± placodioid, thick, puckered and ± folded in ridges, lobed at the margins, bright yellow-green, occasionally yellow and sometimes stained brownish in parts, the surface interspersed with yellowish crystals. Medulla well-developed, not blueing in iodine, dark brown beneath, with rhizine-like hyphal strands extending into the substratum. Prothallus absent. Photobiont unidentified coccoid green algae.
Anamorph: not known.
Teleomorph: ascomata apothecia, to 2 mm diam., initially immersed, arising between the squamules, with a thin crenulate margin, the cortical tissues surrounding the ascomata dark red in section. True exciple soon excluded, dark reddish brown, composed of cells with scarcely distinct lumina. Thalline exciple absent. Hymenium 100-120 μm tall. Hypothecium dark brown, reddish in parts. Interascal tissue composed of thin-walled frequently branching and anastomosing paraphyses 2-3 µm in diam. immersed in a gelatinous matrix, the apical cells slightly inflated, within a dark olive-green to ± black epithecium that is, K–, N+ rose. Asci 50-70 × 14-17 μm, cylindric-clavate, the outer coat K/I+ blue, ± thickened at the apex, with an internal deep blue K/I+ meniscus-like cap, 8-spored. Ascospores (12-)13-17(-18) × 7-10 μm, ellipsoidal, rounded or occasionally broadly apiculate at the ends, initially grey to olivaceous and maturing dark brown, 0- to 1- (to 3-) septate, smooth, thick-walled, the slightly constricted central septum thickened with an internal torus, lacking a distinct perispore.
Chemistry: thallus C–, K–, KC–, Pd+ yellow-orange (rhizocarpic acid and perhaps argopsin).