Flora of New Zealand Series

≡Agyrophora zahlbruckneri var. robusta, Llano Monogr. Lich. Fam. Umbilicariaceae: 61 (1950).

Holotype: New Zealand. Stewart I., Mt Anglem, 900 m, 1.iii.1946, W. Martin 44 – CHR 381013.

Description : Thallus monophyllous to irregularly polyphyllous with numerous, small, congested lobes, orbicular to irregularly and deeply incised, (0.5–)1–2(–4) cm diam.; margins slightly thickened, black-rimmed, entire, sinuous, to variously notched or incised or laciniate, often with sparse to dense, projecting rhizinomorphs. Upper surface brown when moist, brownish black, grey-brown to pale-greyish when dry, coriaceous, smooth, minutely roughened, or here and there white-pruinose to delicately scabrid-areolate (×10 lens), shallowly to coarsely wrinkled centrally at umbo. Lower surface black, pale to dark grey-brown towards margins, to entirely sooty black from margins to centre, minutely roughened to distinctly scabrid-areolate, smooth to shallowly dimpled (reflecting insertion of apothecia on upper surface). Rhizinomorphs pale grey-brown to black, cylindrical to flattened, 0.1–0.3 mm diam., 1–3(–5) mm long, simple to dichotomously or irregularly branched, with or without lateral, knob-like thalloconidia. Umbilicus 2–5(–7) mm diam. Apothecia scattered to crowded, subpedicellate to distinctly pedicellate (pedicel concolorous with thallus and contrasting with disc), round to irregular-flexuous, (0.5–)1–2(–3) mm diam., solitary and widely scattered to densely crowded and distorted through mutual pressure; disc shallowly concave at first, generally plane, rarely subconvex at maturity, black, matt, epruinose, without central sterile tissue; margins prominent, persistent, entire, sinuous to irregular, raised, glossy, black. Epithecium dark-brown, 15–20 μm thick. Hymenium colourless to very pale yellowish brown, (50–)60–80 μm tall. Hypothecium pale yellow-brown, 95–115 μm thick, densely interwoven. Asci broadly clavate 55–65 × 25–35 μm, 8-spored. Ascospores simple, broadly ellipsoidal to ovoid, colourless, brown when over-mature, (16.5–)17.5–22.5(–23.5) × (7–)9–13.5 μm. Pycnidia sparse to abundant, dark red-brown to black, punctiform, 0.1 mm diam. Conidia bacillar, 2–3.5 × 1 μm.

Chemistry : Not tested.

S: Otago (West Matukituki Valley, Rees Valley, Mt Cunningham, Theatre Flat Rockburn Valley). St: (Mt Anglem). On rocks and boulders in subalpine grassland and fellfield, 950–1890 m, associating with Pseudephebe pubescens, Rhizocarpon geographicum, Umbilicaria cylindrica and U. subaprina.

Endemic

Umbilicaria robusta is characterised by: the saxicolous habit; the orbicular to irregularly polyphyllous thallus (1–2 rarely to 4, cm diam.), with rhizinomorphs projecting from margins; a coriaceous, smooth, white-pruinose to areolate scabrid upper surface; a black, minutely roughened to scabrid-areolate lower surface, with thalloconidia and cylindrical to flattened rhizinomorphs 1–3(–5) mm long; distinctly pedicellate apothecia with a smooth, plane, black disc and with thick, glossy margins; and broadly ellipsoidal ascospores, (16.5–)17.5–22.5(–23.5) × (7–)9–13.5 μm.