(Last Modified On 5/9/2013)
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(Last Modified On 5/9/2013)
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Species
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Najas arguta H.B.K.
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PlaceOfPublication
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Nov. Gen. and Sp. PI. 1: 371. 1815.
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Synonym
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Najas tenera Schrad., Gbtt. Gel. Anz. 2: 715. 1821. Caulinia tenella C. G. Nees in Neuwied, Reise Bras. 2: 345. 1824.
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Description
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Plants glabrous, monoecious. Stems 0,3-1.0 mm in diameter, profusely branched, in habit appearing bushy; lower internodes elongate (to 13.5 cm long), the upper internodes shortened (to 7 mm long or less). Leaves 1.2-2.8 cm long; laminas 0.6-1.9 mm wide, acute to acuminate, mucronate, conspicuously serrulate with 15-25 teeth per side, the mucro slightly larger than the lateral teeth, the teeth multicellular, formed by layers of cells decreasing in cell number outward, terminated by a large, sharp-tipped cell; auricles 1.2-3.4 mm wide, wider than the laminas, round to truncate, serrulate with 2-7 teeth per side, the teeth similar in structure to but smaller than those of the laminas. Flowers solitary, the staminate in the upper leaf axils, the carpellate in the lower leaf axils, the in- volucre purple-tinged; staminate flowers 2.0-2.2 mm long, the involucre above the anther abruptly narrowed into a short beak (0.5 mm long), ending in 4 sharp- tipped lobes, the anther to 1.6 mm long, 1-thecate, the filament at anthesis to 1.2 mm long; carpellate flowers 1.7-2.1 mm long, the involucre above the ovary abruptly narrowed into a short beak ending in 3-4 sharp-tipped lobes, the style ending in 2 stigmatic lobes that extend above the involucral beak. Fruit 2.1-2.6 mm long and 0.6-0.8 mm wide, yellowish-white, elongate-fusiform, with a single basally flattened keel-like rib along which the involucre splits, the areolae some- times inconspicuous, longer than broad, to 0.2 mm long and ca. 0.05 mm broad, in ca. 50 longitudinal rows, the end walls raised giving the pericarp wall a papillose appearance; seeds elongate-fusiform, greenish-white with 3 dark bands.
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Specimen
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CANAL ZONE: Chagres River, Dwyer & Robyns 76 (MO, US), Fairchild 2102 (GH, MO); at Juan Mina, Trapido B1022 (GH, NY, UC, US); ca. 2 mi. above Pan Canal, Lazor & Boreham 2913 (FSU, UC); mouth of Rio Moja Polla, near village of Las Guacas, Trapido B1021 (MO, NY). Gamboa, Tyson, Dwyer & Blum 4602 (FSU, MO). Gatun Lake, Duke 8310 (OS). Madden Lake, Woodson & Schery 956 (MO). DARIEN: Rio Pirre, Duke & Bristan 8310 (MO).
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