Caloplaca irrubescens
≡Lecanora irrubescens Nyl., Flora 57: 318 (1874).
Description : Thallus in small patches, of scattered to contiguous areolae, areolae angular or irregularly rounded, to 0.5 mm diam., orange, on a blackish prothallus, often associating with cyanobacteria. Apothecia numerous, scattered, sessile, rounded, disc plane to subconvex, orange to brownish orange. Hymenium colourless, to 100 μm tall. Hypothecium colourless, 60–80 μm thick. Ascospores broadly ellipsoidal, 10–13(–16) × 6–8 μm, septum 2.5–5 μm thick, ⅓ to ½ length of spore.
Chemistry : Thallus K+ red-purple; containing parietin.
S: Otago (Upper Clutha Valley near Luggate). On stones and pebbles among old gold workings, on river terrace; associating with species of Xanthoparmelia. Known also from dry Mediterranean habitats in Europe, Morocco, Turkey, Ukraine, the Himalaya and North America, with a solitary record from Wales in the 19th century but uncollected there since (Laundon 1992; Nimis 1993; Poelt & Hinteregger 1993; Egea 1996; John 1996; Kondratyuk et al. 1996b, 1998; Scholz 2000; Fletcher & Coppins 2001g; Haffelner & Türk 2001; Llimona & Hladun 2001; Nimis & Martellos 2003; Obermayer 2004).
?Cosmopolitan
Illustrations : Wirth (1987: 101; 1995a: 201, fig. 29C; 1995b: 234); Nimis et al. (1992: 71).
Caloplaca irrubescens is characterised by: the saxicolous habit; the orange, areolate thallus on a blackish prothallus; scattered, sessile, orange apothecia; and broadly ellipsoidal ascospores, 10–13(–16) × 6–8 μm, septum 2.5–5 μm thick.
