Pyrenothrix Riddle
Thallus filamentous, brownish-black, effuse, spreading over the substrate, gelatinous spongy when wet, brittle when dry. Filaments c. 1 mm long and 0.1-0.2 mm thick, of entangled fungal hyphae (2.5-4.5 µm thick) surrounding cells of photobiont. Photobiont blue-green, Scytonema. Perithecia minute, pyriform, ostiole minute, indistinct. Asci clavate, 8-spored, bitunicate. Ascospores muriform, ellipsoid, brown or brown-black.
Pyrenothrix is a monotypic genus included in the monogeneric family Pyrenothricaceae Eriksson [ Opera Bot. 60: 144-146 (1981)]. It is discussed by Eriksson ( loc. cit. ), and Henssen [ Ber. dtsch. bot. Ges. 77: 317-322 (1964)]. The sole species P. nigra Riddle, is known from the southern United States and was recently collected in New Zealand by J.K. Bartlett [see Tschermak-Noess et al., Pl. Syst. Evol. 143: 293-309 (1983)].
