Graphidaceae of Central French Guiana

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S. labyrinthica Ach. B32956

Thallus corticolous, epiphloeodal, continuous, very evenly thin, gray green and here and there mottled brownish or pale gray, smooth, flat and thinly corticate, slightly shiny. K+ reddish, P-. Stromata evenly and fairly widely dispersed, abundant, discrete, white with distinctly and suddenly raised margins, more or less constricted at the base, K+ bright yellow, P+ (psoromic?) orange. Lirellae very dense and crowded, short to moderately elongate (up to only about .5 mm), angular often small and triangular or quadrate and split into smaller angular shapes when dry, each lirella surrounded by a distinctly taller white margin, often cracked longitudinally and pale creamy or whitish, crumbling. Disks exposed narrowly (usually less than 0.07 mm) grayish pruinose. Exciple brown to blackish, thinly carbonized laterally and closed narrowly below. Hymenium more or less elliptical in cross-section, rounded below, inspersed with large oil drops, epihymenium and hypohymenium pale I-, brownish. Spores 8/ascus, oblong, brown, thick walled, lumina lentiform, 5-7x9-14µ.

Also examined B32919, B32927