Herb, short-lived perennial, glabrous, to 100 cm tall; rhizome erect present, to 2 cm; stolon absent. Leaves submersed or emerged; emerged leaves pale green, petiole ridged, 6-25.5 x 0.2-0.35 cm, basal sheath to 5 cm long, blade linear-elliptic to elliptic, 6-22.5 x 1.5-4 cm, margin entire, apex acute to acuminate, base truncate to acute, basal lobes absent, veins 3-7, pellucid markings present as short, separate lines; submersed leaves pale green, petiole triangular, 1.5-7.5 x 0.2-0.3 cm, basal sheath 7 cm long, blade linear-elliptic, 7.5-22.5 x 0.3-1.7 cm, apex acute to acuminate, base truncate to acute, margin entire, veins 1-3, pellucid markings present as short, separate lines. Inflorescence racemose, erect, with 4-12 whorls, overtopping leaves, often vegetatively proliferating, 7-40 x 0.4-1.5 cm; whorls with ca. 6 flowers; peduncle slightly ridged, slightly winged, 5-20 x 0.05-0.2 cm; rachis between whorls terete, not winged; bracts longer to shorter than pedicel subtended, separate, delicate, elliptic, to 5 x to 2 mm, membranous, apex acute, not dilated basally; pedicels in flower spreading, in fruit recurved, 0.4-1 x ca. 0.04 cm. Flowers to 1 cm wide; sepals in flower reflexed, 2.5-3 mm long, with ca. 9 veins, not papillose; petals not clawed, ca. 5 x ca. 3 mm; stamens 8-12, filaments ca. 1.5 mm long, anthers versatile, 0.5-1 mm long, apex obtuse; carpels 30 or more. Fruit terete, clavate, 1.8-2.3 x 0.8-1 mm, 3-4-ribbed, without keel, glands 5 or more, circular, between ribs, beak terminal, erect, to 0.5 mm long.
Guianas present, Southern America: Bolivia (Bolivia present); Colombia (Colombia present); Cuba (Cuba present); Honduras (Honduras present); Peru (Peru present); Venezuela (Venezuela present)
In wet ditches and marshes and along shores of lakes and small rivers, from Cuba and Honduras, S to Colombia, Peru, Bolivia, Brazil, and NE to Venezuela and the Guianas; 41 collections examined, including 13 from the Guianas (GU: 1; SU: 5; FG: 5).
Sold under German commercial name "Smalblättrige Amazonas Schwertpflanze" ("Small Leaved Amazon Swordplant."); also cultivated under names "Amazonian Swordplant", or 'E. rangeri', 'E. amphibius', 'E. gracilis', 'E. parviflorus', 'E. bleheri' and 'E. parviflorus tropica'.