Hyphal strands: superficial, black, partly confluent, with a ±radial arrangement, forming orbicular or irregular compact groups sometimes resembling a rosette; strands: dark brown, plurihyphal (stromatic), formed by numerous, 8-30 rows of cells, simple or scarcely ramified, frequently widening towards their apex, flat or slightly convex, about 6090 µm long and 25-55 µm wide, with a granular surface; Ascomata: black, superficial, frequently arising towards the center of each group of hyphal strands, connected to 1 or several hyphal strands, subglobose or irregular, 60-100 µm long and 50-70 µm wide; internal structure: wall of external cells: dark brown, with a granular surface; wall of internal cells: pale brown, cells mostly 4-5 µm in diam.; centrum: I+ pale red, K/I+ blue; asci: several per section of ascoma, globose or subglobose, 20-25 x 15-17 µm, 68-spored, I-; ascospores: hyaline initially but soon brown, initially 1-septate and ellipsoid, later submuriform, 3-7 celled, broadly obovate, markedly constricted at the equatorial septum, 11-16 x 7-10 µm, without a visible halo, with a granular surface on the oldest ones.; Host: on the thallus and apothecia of Buellia species, without causing any apparent damage; World and Sonoran distribution: Chihuahua.; Notes: Lichenostigma ampla is very distinctive by its wide hyphal strands and submuriform ascospores; typically, the strands are grouped in dense compact groups sometimes a rosettes. Lichenostigma diploiciae, a Mediterranean-Macaronesian species growing on Diploicia subcanescens, has also submuriform ascospores, but its hyphal strands are much narrower (about 9-20 µm thick, and only with up to 5 rows of cells), and its hyphae are not grouped in rosettes, but rather scattered or loosely aggregated.
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