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Lecanora melaena (Hedl.) Fink
Family: Lecanoraceae
Lecanora melaena image
Bruce Ryan  
Thallus: absent or crustose and very sparse [to rimose-areolate according to Fink (1935)]; prothallus: not visible; areoles: dispersed to grouped, 0.5-1 mm across, irregularly ±round to weakly crenate, plane to irregularly convex; surface: light to pale yellow in herbarium [greenish gray to ashy according to Fink (1935)], esorediate cortex: densely inspersed with fine yellow-brown granules (soluble in K, insoluble in N), the lower part +with dead algal cells, overall c. 50 µm thick, the upper 10-20 µm composed of unoriented hyphae 3-4 µm wide with narrow lumina, appearing somewhat cellular; epinecral layer: c. 510 µm thick medulla: white, with fine colorless granules and occasional coarse colorless crystals (both insoluble in K), the hyphae unoriented, distinct, 2-3(-5) µm in diam. with narrow lumina; algal layer: continuous; algae 8-12 µm in diam. Apothecia: following cracks or depressions in the rock, scattered to very numerous and crowded to overlapping (forming clusters to c. 3 mm across), sessile on the substrate, constricted at the base, 0.5-1.2 mm in diam. disc: greenish gray to black, or becoming light orangish yellow to light yellowish brown with pale gray tinge, plane to convex, occasionally undulate or concave due to crowding, mostly dull, becoming very finely roughened and cracked, with glaucous appearance when wet margin: concolorous with thallus or more white, entire to flexuous or coarsely crenate, level with disc, +gradually excluded, 0.1-0.15 mm wide, with an indistinct parathecial ring though discs are sometimes darker next to margin amphithecium: present, with a well developed, +continuous algal layer (25-40 µm thick) in lower part of margin and extending below the hypothecium, with intricate, weakly radiating, hyphae c. 3 µm wide and with narrow lumina, medulla absent from margin but present under the apothecium, filled with fine yellow-brown granules, corticate; cortex: hyaline but densely inspersed with fine yellow-brown granules (soluble in K, insoluble in N), c. 50 µm thick at top, up to 100 µm thick near base parathecium: hyaline, composed of conglutinated, unoriented hyphae 4-5 µm wide with narrow lumina, 20-30 µm thick, similar in structure to the hypothecium epihymenium: densely inspersed with fine pale green to yellow-brown granules which partly penetrate to 20-25 µm deep along the paraphyses, 10-15 µm thick hymenium: hyaline, 50-60 µm tall; paraphyses: +coherent, c. 1.5 µm wide, simple or occasionally forked; tips: clavate to capitate, 3-5 µm wide, hyaline or green, intensified green in K, colorless in N; subhymenium: +distinct, hyaline to pale yellow-brown, not inspersed, c. 25 µm thick; hypothecium: 40-50 µm thick asci: clavate, c. 40 x 13 µm, 8-spored ascospores: hyaline, simple, ellipsoid to oblong-ellipsoid, sometimes narrowing towards one end, often slightly curved, 10-14 x 4-5 µm [8.5-11.5 x 5-6.5 µm according to Fink, 1935] Pycnidia: occasional, immersed, 50-75 µm in diam., with green-gray ostioles conidia: filiform, distinctly curved or hooked, 17-22 x 1 µm Spot tests: thallus and apothecial margin K-, C-, KC-, P- Secondary metabolites: not tested; cortex presumably with usnic acid. Substrate and ecology: on acidic rocks, alpine World distribution: western North America, east to Minnesota, south to California and possibly Europe Sonoran distribution: reported from Arizona by Rudolph (1953); material not seen by us. Notes: The description of L. melaena given here is based on specimens collected by Ryan from Colorado and Washington State, which differ somewhat from the description given by Fink (1935), in the development and color of the apothecia, and size of the spores. Although L. polytropa is very similar, and according to Poelt (pers. comm.) the discs of that species can become pale green in strongly exposed alpine sites (var. melaenoides Vain.), at least in the collections from Colorado and Washington State, the two species (both with little or no thallus) can be distinguished when growing side by side, by the thinner, apothecial margins of L. melaena, which are level with and contrasting in color with the discs even when the latter are pale yellow. In the Ryan collections, the lowermost parts of the apothecial margin and area below the medulla show a 50-60 um thick layer of green-black (K+ green, N+ red-violet) thallospores 5-8 um diam. (probably belonging to a conidia-producing microcolonial fungus that forms numerous tiny patches on the rock).