Alternanthera philoxeroides
Content
Description
Perennial aquatic herb to 1 m; stems hollow, striate, rooting at lower nodes, pressing to ca. 1.3 cm wide. Petiole 1-16 mm long; blade lanceolate, oblanceolate, oblong-lanceolate or narrowly ovate, 2-10 x 0.5-2.7 cm, entire or sometimes subdenticulate, apex obtuse to acute, base cuneate and tapering to petiole, subcarnose, glabrous above, glabrous or subglabrous beneath. Inflorescence usually axillary (sometimes and/or terminal), 1.0-5.5 cm long pedunculate, solitary heads; heads hemispherical or subglobose, 10-18 x 10-18 mm; bracts and bracteoles subequal, ovate, 1-2 mm long, acuminate, bracteoles much shorter than tepals, glabrous, central vein not prominently raised. Tepals white, oblong-lanceolate, 5-6 x 1.5-2.5 mm, acuminate, mucronulate, denticulate at apex, glabrous, faintly veined; stamens 5, pseudostaminodia exceeding stamens, lacerate; style about twice as long as stigma, stigma capitate. Utricle reniform, 1.0 x 1.0-1.5 mm.
Distribution
Guianas present, Tropical and subtropical South America present
Tropical and subtropical South America (adventive elsewhere); 23 collections studied, all from the Guianas (GU: 4; SU: 14; FG: 5).