Erect to spreading, semiaquatic, decumbent herb, 20-25 cm tall. Stem obtusely quadrangular, sulcate, angles and interpetiolar lines sometimes fimbriate, cystoliths inconspicuous. Leaf sessile; blade linear-lanceolate, 2.5-5.5 x 0.5-1 cm, apex acute, base attenuate and decurrent on petiole, glabrous on upper surface, lower surface primary and secondary veins pilose with rather thick trichomes; secondary veins 5-7 pairs. Inflorescence of opposite or alternate dichasia, 1-flowered; bracts subtending lateral flowers spathulate, 7 x 15 mm, basally sparingly pilose, margin ciliolate. Flowers subsessile; calyx deeply 5-lobed, lobes equal, narrowly linear, 6 x 0.5-0.7 mm, primary veins hirtellous, margin densely ciliate; corolla mauve, 8.5-9 mm long, glabrous without, lower half of tube cylindrical, upper half enlarged, funnel-shaped, upper lip erect, 3 mm long, 2-lobed, lobes 1.2 mm long, lower lip 3-lobed, lobes 2.2 mm long; lower pair of stamens inserted at middle of corolla tube, shorter pair inserted at tip of corolla tube, sometimes with exceedingly unequal thecae, filaments free at base, 3.8 and 1.5 mm long respectively, enlarged basally and shortly ciliate, anthers obtuse at tip, 1.1 and 0.7 mm long respectively, staminode clavate-filiform, 0.6 mm long, inserted between shorter pair of stamens; disk annular; ovary glabrous, 1.8 mm high, each locule with about 6 ovules, style 6-6.7 mm long, glabrous, anterior stigma lobe filiform, 0.8 mm long, posterior lobe minute. Capsule not seen.
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