Diploschistes actinostomus
≡Verrucaria actinostoma [Pers. ex] Ach., Lichenogr. universalis: 288 (1810).
Description : Thallus crustose, uniform, rather thin, areolate, areolae 0.5–1.5 mm diam. Upper surface whitish grey to grey, smooth, glossy to matt, epruinose. Apothecia perithecioid, immersed, to 3 mm diam.; disc blackish, plane. Proper exciple to 70 μm thick. Hymenium 120–160 μm tall. Asci cylindrical to clavate, 4–8-spored. Ascospores brown, muriform, ellipsoidal, 16–32 × 10–20 μm, 4–6 transverse septa, 1–3 longitudinal septa per transverse segment. Pycnidia immersed. Conidia bacillar, 4–7 × 1 μm.
Chemistry : K−, C+ red, Pd−; containing lecanoric acid (major), diploschistesic acid (tr.), orsellinic acid (tr.), atranorin (tr.), chloroatranorin (tr.).
S: Otago. On base-rich siliceous rocks in open, sunny sites. Known also from Europe, Macaronesia, Asia, North America, West Indies, North Africa, South Africa, Socotra, India, Nepal and Australia (Lettau 1937; Lumbsch 1989, 2002; Pant & Upreti 1993; Guderley & Lumbsch 1996; Lumbsch & Elix 2003; McCarthy 2003c, 2006; Nimis & Martellos 2003; Mies & Schultz 2004).
Cosmopolitan
Illustrations : Lettau (1937: tab. 4, figs 47–49); Lumbsch (1989: 156, fig. 12); Pant & Upreti (1993: 36, fig. 2A).
Diploschistes actinostomus is characterised by: the saxicolous habit; the grey-white to greyish thallus; perithecioid ascomata; 4–8-spored asci; ellipsoidal ascospores, 16–32 × 10–20 μm; and lecanoric acid in the medulla. Poorly developed forms are distinguished from P. euganeus, which has no secondary chemistry and broadly ellipsoidal ascospores.
