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DescriptionLife habit: lichenized; Thallus: foliose, heteromerous, dorsiventral, lobate, irregularly spreading, 2-10(-15) cm in diam., loosely adnate or appearing unattached, or attached to substrate by a root-like holdfast developing a distinctive, erect, terete or flattened stalk from which arise monophyllous to polyphyllous lobes; lobes: irregularly branching, rounded to imbricate to variously incised, often lacerate-notched, tough, coriaceous to fragile, thin to thick; upper surface: black, brown, gray, olivaceous, or green, continuous, smooth, wrinkled or obscurely ridged, sometimes shallowly pitted or faveolate, glossy or dull, with or without isidia, maculae, phyllidia, soredia, tomentum or cephalodia, without goniocysts and never with pseudocyphellae; upper cortex: paraplectenchymatous, composed of anticlinally arranged, ±isodiametric, thick-walled cells; medulla: loose, white, never yellow; photobiont: primary photobiont cyanobacterial (Nostoc) or chlorococcoid (Chlorella-like); accessory photobiont present or absent; lower cortex: similar in structure to the upper cortex; lower surface: pale or dark, glabrous or tomentose (hyaline to brown, patchy or continuous, formed by bundles of elongated hyphae, attaching to substrate), cyphellate; cyphellae: white or rarely yellow or pale red, round or to irregular, with a well-defined, often raised margin, with the floor of the cyphellae bounded by a membrane and not composed of projecting medullary hyphae; Ascomata: apothecial, often absent or sparsely developed, hemiangiocarpic, laminal, rarely marginal, sessile or pedicellate; disc: brown or red-brown, round, dull or glossy, usually concave, epruinose; margins: well-developed, entire or crenate-striate or denticulate, sometimes with projecting, silky hairs; exciple: pale yellowish buff, pale brown or pink; epihymenium: yellow-brown to red-brown, unchanged in K, 5-15 µm thick; hymenium: hyaline, I+ blue, 90-140 µm tall; paraphyses: simple, slender, septate, unbranched, not anastomosing, swollen or not and sometimes pigmented at apices; hypothecium: pale or dark, hyaline to yellow-brown or red-brown, opaque, composed of densely interwoven hyphae; asci: cylindrical to clavate, shorter than paraphyses, Peltigera-type, unitunicate, with an amyloid (I+ blue) cap in the tholus, 8-spored; ascospores: hyaline to pale to dark brown or olivaceous, simple at first but soon becoming polaribilocular to transversely 1-3(5-7-)-septate, ellipsoid-fusiform, rounded or pointed at apices, with smooth walls; Conidiomata: pycnidial, laminal, immersed, punctate to subglobose, Lobaria-type, with dark-brown or blackened walls at the ostiole but paler below; conidia: hyaline, short, bacilliform to sublageniform, borne laterally and terminally on simple to slightly branched conidiophores; Secondary metabolites: lacking or rarely with K+ pigments in medulla and/or cyphellae, cyanobacterial species produce methylamines that impart a characteristic fishy smell when moist; Geography: temperate to tropical; Substrate: on bark, lignum, soil, detritus, or non-calciferous, siliceous and volcanic rocks, in humid, shaded, to moderately open, forested areas.; Notes: Sticta is characterized by the presence of cyphellae on the lower surface, emergent apothecia with hyaline or brown 1-3-septate (rarely 5-7-septate) or polaribilocular ascospores, and a notable lack of secondary chemistry in sharp contrast to Pseudocyphellaria. Of the 12 species of Sticta collected in the Sonoran region all, except one, have cyanobacteria as their primary photobiont, and have a characteristically fishy smell (because of soluble amines), especially when wet, but also distinctly noticeable in many herbarium specimens. These cyanobacterial species are most commonly found in sites of high humidity and moderate to deep shade.