Rhizocarpon purpurescens
Description : Thallus areolate, creamish white to grey. Areolae flat, 0.4–0.6 mm diam., dispersed or contiguous. Medulla I−. Apothecia black, lecideine, orbicular, (0.5–)0.7–0.9 mm diam., sessile, plane to convex, margin thin and scarcely raised, 0.03–0.04 mm wide. Epithecium dark blue-black (K−, N+ red), 15–20 μm thick. Hymenium vertically streaked red-brown (K+ purple, N–), 130–150 μm tall, I+ blue. Paraphyses slender, 1.5–2 μm thick, branched and anastomosing, conglutinate, swollen at apices to 5–6 μm with a dark blue-black (K−, N+ red) cap. Hypothecium thin, 35–50 μm thick, mid- to dark-brown (K−, N−). Asci cylindrical to clavate, 85 × 35 μm. Ascospores hyaline at first, becoming blue-black (K−, N+ red), submuriform with 1 transverse and 3–5 longitudinal septa, (21–)24–30(–34) × 12–14 μm, halonate, halo 7–8 μm thick in young ascospores, thinner in mature spores. Pycnidia not seen.
Chemistry : Thallus K+ yellow or red, C−, KC+ red, Pd+ yellow or orange; containing stictic and/or norstictic acids.
S: Canterbury (E of Hanmer Springs). C: (Mt Honey, Mt Azimuth). On rocks in farmland, and in subalpine fellfield, associating with Candelariella sp., Fuscidea asbolodes and Pertusaria sp. Known also from Kerguelen (Fryday 2004a).
Austral
Rhizocarpon purpurescens is characterised by: a creamy white thallus containing stictic acid; a dark blue-black (K−, N+ red) epithecium; a red-brown pigment in the hymenium turning purple in K; I− medulla; and halonate, colourless to blue-black, submuriform ascospores.
