Pyrenidium Nyl.
Type : * Pyrenidium actinellum Nyl.
Description : Lichenicolous. Ascomata perithecia, arising singly or loosely aggregated, immersed to erumpent, subglobose to obpyriform, black, ostiolate, walls composed of 2–4 layers of dark-brown pseudoparenchymatous cells. Hamathecium of paraphyses (pseudoparaphyses), persistent, branched and anastomosing. Asci fissitunicate, cylindrical, 4–8-spored. Ascospores broadly ellipsoidal, 3-septate (rarely 2- or 4-septate), constricted at septa, dark-brown but with apical cells often paler brown, smooth-walled, without a gelatinous sheath.
Pyrenidium is a genus of c. 8 species, all of which are lichenicolous, widely distributed in tropical and extra-tropical regions, and included in the family Dacampiaceae (Lawrey & Diederich 2003; Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005). The taxonomic history of the genus is discussed in Hawksworth (1983b) and Matzer (1996: 146–147). One species is recorded from New Zealand (Kondratyuk & Galloway 1994) and an undescribed species is also known from Xanthoparmelia semiviridis (P. Diederich pers. comm.).
