Graphidaceae of Central French Guiana

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Graphis striatula (Ach.) Sprengl. B 18699b

Thallus thin, corticolous, epiphloeodal, thickened slightly in broad raised areas near apothecia, mineral gray to whitish with creamy tones, surrounded by a narrow brownish interaction zone, mostly smooth and slightly shiny, K+ yellow, P?, about 1 cm across. Apothecia sessile, evenly dispersed with low thalline margin, bacilliform to longer, but evenly broad and parallel-sided, curving or rarely straight, .5-1.5 mm long and rather consistently .16 mm wide, not constricted at base, black exciple exposed almost to base, except when quite young, shallow striae visible superficially, not extending the length of the ascoma, exciple dimidiate, carbonized, crenate laterally. Hymenium ovoid or cordiform in cross section, hyaline, not inspersed. Spores 8/ascus, 4x38µ, more or less broadly fusiform, lumina lentiform, I+ blue, 16 locular. No lichen substances.

Also examined B 25777, with apothecia to 6 mm long, often 1x branched, with thallus ca. 3 cm across, spores 8x42-45µ; B 18622, both with stictic acid aggregate.