Life Habit: lichenized; Thallus: fruticose, erect, decumbent (prostrate), subpendent or pendent, markedly elongate, attached by a basal holdfast; branches: ± terete, or occasionally somewhat expanded and dorsiventrally compressed, or angular to foveolate towards the base and at branch axils; surface: greenish yellow or occasionally streaked greenish-black, or in one species (A. nigricans) grayish to pinkish or brown-black, continuous, generally smooth, occasionally becoming striately ridged towards base and axils; pseudocyphellae: always present, often conspicuous, fusiform, white, flat to markedly raised; soredia: present or absent; isidia: absent (but pseudocyphellae becoming sorediate and bearing spinules in one species); true lateral spinules: absent; cortex: composed of longitudinal, periclinal, arachnoid, conglutinated hyphae immersed in ± large amount of matrix; medulla: loose, arachnoid; hyphae: longitudinal, distinctly segmented, usually ornamented; cell walls with isolichenan, Cetraria-type lichenan, and sometimes traces of intermediate types of lichenan; photobiont: primary one a trebouxioid alga, secondary photobiont absent; Ascomata: apothecial, lateral, sometimes appearing geniculate owing to the death of the branch distal to them, sessile, slightly stalked, circular; thalline exciple: persistent and often markedly incurved, concolorous with thallus; disc: concave, brown to dark brown or black; exciple: gray or hyaline; hymenium: hyaline below, brown, green, blue-green, gray above, I+ very strongly blue; paraphyses: 1.5-3 micro meters wide, somewhat branched and anastomosing, the tips weakly pigmented, 70-140 micro meters; hypothecium: hyaline or pale, 20-40 micro meters, over an algal layer; asci: clavate-oval, 65-130 x 25-50 micro meters, Lecanora-type; wall: 6-12 micro meters thick; tholus: I+ blue, the ocular chamber and axial body short and broad, 2-4 (-8)-spored; ascospores: simple, broadly ellipsoid, 20-45 x 12-25 micro meters; wall: 3-4 micro meters thick, at first hyaline, becoming pale brownish, grayish to dark brownish or blackish at maturity, smooth, with distinct, pale, gelatinous outermost layer, I-; Conidiomata: pycnidial, usually rare, (sub-) marginal-(sub-)terminal, immersed in thalloid warts; conidia: bacilliform, pleurogenously formed, 7-8 x 0.8 micro meters; Secondary metabolites: cortex usually with usnic acid (except in A. nigricans); medulla and/or cortex often with orcinol and ß-orcinol depsides and depsidones and an unidentified K+ red, C+ green-black metabolite occurs in the cortex of the basal parts of the thalli of most species; Geography: circumbipolar, arctic-alpine to boreal-montane; Substrate: on bark, wood, soil, or detritus.; Notes: Alectoria is readily separable from other genera, including Bryoria and Pseudephebe, by its characteristic yellow-green color (due to usnic acid) in most species, the cortical structure and the abundance and structure of the pseudocyphellae. It differs from most species of Usnea (which are also yellow green due to usnic acid) by the lack of a central strand. According to Tucker and Jordan (1978), the reports of A. ochroleuca (Hoffm.) A. Massal. from southern California by (Orcutt 1907 & 1909, as Usnea ochroleuca Fr.) and Hasse (1913) are based on misidentifications (presumably not species of Alectoria at least in the modern, more restricted sense).
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