Lecanora crenulata
Description : Thallus immersed, inconspicuous. Apothecia sessile, constricted at base, rounded 0.2–0.6 mm diam.; scattered, never crowded, disc plane to subconvex, dark-grey, usually distinctly white- or grey-white-pruinose. Thalline exciple prominent, 0.05–0.15 mm thick, persistent, white, well-developed, regularly deeply crenate (like a pie crust). Hymenium 50–70 μm tall. Ascospores 6–10(–15) × 4–6(–7) μm.
Chemistry : TLC−, all reactions negative.
S: Nelson (Mt Owen), Otago (Roxburgh), Southland (Castle Rock, Clifden). On limestone, mortar, old concrete paths etc. Known also from Great Britain, Europe, Scandinavia, North and South America (Fröberg 1989, 1997; Purvis et al. 1992; Nimis 1993; Santesson 1993, 2004; Esslinger & Egan 1995; Poelt et al. 1995; Scholz 2000; Laundon 2003; Nimis & Martellos 2003; Ryan et al. 2004b: 213–214).
Cosmopolitan
Illustrations : Foucard (1990: pl. 138); Dobson (1992: 171; 2000: 192; 2005: 220); Poelt et al. (1995: 305, fig. 5I; 315, fig. 7B; 329, fig. 9D); Fröberg (1997: 32, fig. 1C).
Lecanora crenulata is characterised by: the saxicolous habit (basic substrata); dispersed apothecia on a largely invisible thallus; the discs a characteristic dark-grey, often white-pruinose, surrounded by prominent, white margins that are often (but not always) radially cracked and deeply crenate, resembling a pie crust; and a negative chemistry.
