Flora of New Zealand Series

≡Segestrella cruenta Körb., Denkschr. Schles. Ges. Vaterl. Kultur: 237 (1853).

Description : Thallus superficial, filmy, dark-brown or brownish or greenish grey, ±gelatinous when wet, minutely areolate, effuse or with a delimiting thin, black prothallus. Perithecia prominent, covered by a thin layer of thalline tissue (except at ostiole), 0.3–0.6 mm diam., ¼–½-immersed; exciple pale- to dark-brown, 400–600 μm diam.; involucrellum black, 500–800 μm diam. Ascospores 8 per ascus, colourless to pale- to medium-brown, often somewhat reniform, 50–80 × 25–40 μm.

Chemistry : TLC−, all reactions negative.

S: Westland (Arthur's Pass). On damp siliceous rocks (with species of Placopsis such as P. rhodophthalma). First collected in New Zealand by Dr Richard Harris in January 1971 (Fryday 2000a: 37). Elsewhere known from periodically inundated to ±submerged rocks along streams and lake margins in arctic Eurasia, Central and Western Europe, North America, New South Wales and Tasmania (Purvis & James 1992d; McCarthy 2001e: 172; 2003c; 2006; Nimis & Martellos 2003; Santesson et al. 2004).

Cosmopolitan

Illustrations : Swinscow (1971: 110, fig. 17); Dobson (1992: 273; 2000: 314; 2005: 353); Valcárcel & Carballal (2002: 251, fig. 1A).

Polyblastia cruenta is characterised by: the saxicolous habit; the thin thallus; large, prominent perithecia; and pale-brown, muriform ascospores, 50–80 × 25–40 μm.