Graphidaceae of Central French Guiana

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Graphis cf. sphaerosporella Nyl. H34001

Thallus corticolous, uniform, crustose, thin and brittle, often flaking and irregularly raised from substrate in flaps or ridges laminally, but closely and tightly appressed to the substrate at margins. Hypothallus white to tan, loosely woven, fan-like spreading irregularly up to 0.8 mm wide or narrow and black, entire and glossy at border of another thallus. Thallus bright yellowish green to pale yellowish green to grayish green, irregularly rugulose and broken to minutely undulate with prominent narrow ridges, subnitid, K+ reddish, P+ yellow (psoromic?). Distinct prosoplectenchymatous layer present throughout except atop stromatic tissue. Ascomata abundant, immersed, appearing fissurine with white farinose margins, bordered by lateral cracks and covered in broken thalline veil. Disposed variously from remote and long-flexuose loosely asteriform to tightly packed on more or less well-developed stromatic tissue, often within the same thallus. Margins raised so ascoma appearing sessile, younger ascomata pointed, tapering narrowly and slowly breaking thought medulla. Lirellae commonly up to 10 mm long, even, flexuose, dichotomously long-branching repeatedly, forming large diffuse asteriform ascomata intricately interwoven and not separated by corticate thallus, but immersed in weakly raised stromata. Disks evenly narrowly to broadly exposed, grayish to white-pruinose (0.03-0.14 mm), often confluent, and uneven, contorted and short-branching when stromatic, apices long tapered, sharp pointed (long acuminate). Exciple complete below, dark brown to completely carbonized, quite thick below, narrow laterally, dark brown and sometimes appearing striate-crenate. Hymenium hemispherical in transverse section with brownish epihymenium. Paraphyses dense, straight, septate, and apically expanded tipped with a narrow rounded rhomboid 2-celled small-papillate ornamented apex, I-. Spores 8/ascus, mostly 4-locular (rarely submuriform with one medial cell once-divided), mostly thin-walled and ± fusiform to narrowly oblong I+ weakly blue, 6x12µ, mostly apparent only between lumina. Lumina more or less round or tapered apically. Psoromic acid? and unknown.

Also examined H 33821, H34037, B 18894, H 33809, H 33245, H 33590, H 33411, H 33718, H 33839, H 34120, B25459, H 33333, H 33461, H 33551, H 34011 Although this description and these specimens are close to the type, they differ from it in having quite different spores: Sphaerosporella Nyl. (type material at NY) has spheroid to slightly elongate cells with thick walls, contrary to the Fr. Guiana collections here with thin-walled, fusiform to ovoid or oblong spores.