Acarospora umbilicata
Description : Thallus continuous, of scattered to contiguous, convex, densely white-pruinose areolae, 0.5–12.5 mm diam. Apothecia 0.5 mm diam, or less, 1–5 per areola, often coalescing, disc concave, brown-black, thalline exciple inconspicuous. Hymenium 85–110(–135) μm tall. Ascospores 4–5 × 1.5–2 μm.
Chemistry : Thallus K−, C+ red, KC+ red, Pd−; containing gyrophoric acid.
S: Canterbury (Weka Pass). On limestone in railway cutting. Known also from Great Britain, Europe, Scandinavia, Israel, Morocco, the Canary Is and Madeira (Magnusson 1929, 1936; Purvis et al. 1992; Nimis 1993; Santesson 1993; Scholz 2000; Coppins 2002b; Nimis & Martellos 2003; Temina et al. 2005).
Bipolar
Illustrations : Wirth (1987: 38); Dobson (2000: 47; 2005: 53).
Acarospora umbilicata is characterised by: the saxicolous (limestone) habit; the densely white-pruinose, areolate, thallus; concave, brown-black apothecial discs; and gyrophoric acid (C+ red).
