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(Last Modified On 6/17/2013)
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(Last Modified On 6/17/2013)
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Subspecific
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Bidens riparia var. refracta (Brandegee) 0. E. Schulz
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PlaceOfPublication
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Symb. Ant. 7: 132. 1911.
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Synonym
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Bidens refracta Brandegee, Zoe 1: 310. 1890. TYPE: Baja California, collection not designated.
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Description
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Erect, branched herb to 1 m tall; stems sometimes stout, drying conspicuously striate, glabrate. Leaves opposite, mostly trifoliolate, occasional leaves 7-foliolate or bipinnate, to 7 cm long, leaflets mostly 2-3 cm long, ovate, apically acuminate, basally truncate to obtuse, serrate, pinnately veined, often reticulate beneath, sparingly pubescent with short weak hairs; petiole ca. ? as long as the leaflet, slender, glabrate, slightly expanded and clasping at the base. Inflorescence an open aggregate of terminal and subterminal heads; peduncles to 10 cm long, striate, glabrate; bracts foliaceous; bractlets mostly 1 or 2, alternate, linear or compound. Heads mostly radiate; involucral bracts in 2 dissimilar series, the outermost ca. 8, linear, ca. 5 mm long, green, glabrate, the innermost broadly lanceolate, membranous or indurate, dark, glabrous, the margins scarious imbricate; receptacle pubescent; paleas resembling the innermost involucral bracts but narrower; ray florets inconspicuous, the corolla ?yellow, the limb drying prominently 5-9-nerved, apically minutely notched, 3-4 mm long, the tube ca. 1 mm long; disc florets numerous, the corolla 4-5 mm long, the tube puberulent, the limb cylindrical, angled, the angles with prominent dark veins, the 5 lobes with dark nerves, glabrous, the anthers dark, basally subauriculate, the appendages narrow, ovate, dark, the style with 4 dark nerves, the branches flattened, apiculate, pilose, the style base immersed in the short, cylindrical, apically sinuate nectary, the ovary elongate, angled, pubescent, the pappus of ca. 4 stout, retrorsely strigose awns. Achene dark, linear, slightly outcurving, ca. 1.5 cm long, conspicuously striate, glabrous or puberulent apically; the outermost achenes densely tomentose with ascending hairs, pappus of ca. 4 stiff, spreading, retrorsely strigose, 3-4 mm long awns.
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Habit
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herb
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Distribution
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This species ranges through Central America and northern South America, occurring as a lowland weed of ruderal or disturbed situations.
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Note
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B. riparia is distinct from B. bipinnata var. cynapiifolia to which it is closely related in its trifoliolate rather than pinnate leaves, its serrate rather than saliently toothed leaflets, and its larger achenes with relatively shorter awns. Although radiate, the head may appear disciform. Sherff (1955) and Schulz (1911) recognized two varieties under B. riparia, the first writer because of the degree of division of the leaves, a feature which appears to vary on different parts of a single plant, and the second writer because of the degree of pubescence of the achenes.
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Specimen
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CANAL ZONE: Balboa, Standley 26078 (US). Near Gatun, Standley 27332 (US). Near Juan Franco race track, Standley 27800 (US). HERBERA: 10 mi S of Ocui, Tyson et al 2836 (MO). LOS SANTOS: 3 mi S of Carreta, ca. 5 mi S of Las Tablas, Burch et al. 1239 (MO). PANAMA: 1 mi E of Tocumen Airport, Blum & Tyson 1963 (MO). Vera Cruz, Lewis et al. 2997 (MO). Saboga Island, Pearl Islands, Tyson & Loftin 5120 (MO).
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