Melanohalea exasperatula (Nyl.) O. Blanco, A. Crespo, Divakar, Essl., D. Hawksw. and Lumbsch — Overview

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Description

 Thallus: loosely adnate to adnate, appressed throughout or more often somewhat raised at the periphery, foliose, up to 5 cm diam., lobate; lobes: broadly rounded, contiguous to ± imbricate, (l-) 2-5 mm broad, ± flat but often with reflexed margins; upper surface: pale olive-green to dark olive-brown or red-brown, smooth to slightly and irregularly wrinkled or occasionally ± shallowly and reticulately pitted; often very oily-shiny, especially near the periphery, central areas (and rarely the lobes as well) becoming ± dull, occasionally with a scattered, light pruina; without pseudocyphellae; isidia: arising as small hemispherical to spherical papillae, enlarging to form distinctly inflated, clavate to spatulate (rarely spherical), 0.3-1 (-2) mm long, remaining simple or sometimes becoming notched or bifurcate at the tip; lower surface: pale tan to dark brown or rarely blackening, uniformly colored or often mottled, ± flat and smooth to irregularly or reticulately wrinkled, somewhat shiny to dull, especially inward; moderately rhizinate, the rhizines ± concolorous with the lower surface or paler; Apothecia: uncommon, up to 3 mm diam., ± sessile, weakly concave or flattening, margin at first entire, becoming crenate or crenate-papillate; asci: clavate, 8-spored; ascospores: broadly ellipsoid to almost subglobose, 8-10.5 x 5.5-8 µm; Pycnidia: not seen; Spot tests: cortex K-, C-, KC-, P-, HNO3-; medulla K-, C-, KC-, P-; Secondary metabolites: none detected.; Substrate: bark or wood, rarely on rocks; World distribution: western and northern North America, Europe, Asia; Sonoran distribution: known from only three Arizonan collections on fir or spruce in mixed conifer forest above 2800 m.; Notes: This species is still most frequently confused with M. elegantula, the only other isidiate species with a C- medulla that occurs in the study area. The two are sometimes found growing together, although M. elegantula is the much more common of the two. Melanelia elegantula is easily distinguished by the less shiny thallus with pseudocyphellate papillae near the margin, and the more cylindrical, usually branched isidia. 

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© Lichen Unlimited: Arizona State University, Tempe.

Source: Lichen Flora of the Greater Sonoran Desert Region

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