Roccellinastrum flavescens
Description : Thallus distinctly byssoid, in small, swollen to flattened, cushion-like clumps, or spreading in irregular tube-like patches, 1–3 cm diam., investing leaf scales and attached by cottony threads. Upper surface pale greenish white when moist, whitish when dry, minutely granular-uneven, to fibrous or sublobulate in parts, becoming cottony-eroded below. Apothecia scattered to crowded, marginal, protruding, attached to thallus by a short stalk, pale pinkish when fresh, fading to whitish on storage, swollen, globular to shallowly indented, immarginate, 0.1–0.8 (–1) mm diam., surface smooth or minutely pruinose. Epithecium pale yellowish brown, granular, 3–5 μm thick, decolourising in K. Hymenium colourless, 20–25(–30) μm tall. Hypothecium opaque, pale yellowish brown, 15–25 μm thick, decolourising in K. Asci clavate, 13–20 × 5–6.5 μm, 8-spored. Ascospores uniseriate to partially biseriate in ascus, globose, 3–3.5 μm diam.
Chemistry : Thallus K−, C−, KC−, Pd+ red; contaning protocetraric acid (major), usnic acid (trace), and virensic acid (trace) (Kantvilas 1990a: 82).
N: Wellington (Tongariro National Park). On living leaves of Libocedrus bidwillii (Galloway & Kooperberg 2006). Known also from Tasmania (Kantvilas 1990a, 2004c; Kantvilas & Jarman 1999).
Australasian
Illustrations : Kantvilas (1990a: 81, fig. 1); Kantvilas & Jarman (1999: 139); Lumbsch et al. (2001: 22); Flora of Australia Vol. 56A (2004: xvi, pl. 21).
Roccellinastrum flavesens is characterised by: the pale-green to green-white, cushion-like, byssoid thallus anchored to the substratum (living leaves of Libocedrus bidwillii) by cottony threads; marginal, protruding, pale-pink, globular apothecia that are attached to the thallus with short stalks; 8-spored asci containing globose ascospores, 3–3.5 μm diam.; and protocetraric acid (Pd+ red) as the major secondary metabolite. The yellowish colour (usnic acid) reported for Tasmanian populations (Kantvilas 1990a, 2004c) was not seen in the New Zealand specimens found.
