Herbs, perennial, from elongated rhizomes. Stems procumbent to erect, (10-)25-40(-65) cm tall, 4-angled, mostly slightly retrorsely aculeolate, hirtellous at nodes. Leaves on main stems in whorls of up to 6(-8), subsessile; blade drying papery, blackish or green, narrowly obovate to oblanceolate, (12-)18-28(-50) × (3-)5-10(-15) mm, with sparse antrorse microhairs adaxially, moderately retrorsely aculeolate abaxially on vein and at leaf margins, base acute to cuneate, margins flat to thinly revolute, apex acute, obtuse, or rounded and abruptly mucronate; vein 1. Inflorescences with axillary and terminal cymes on upper 2 or 3 nodes, mostly 2-8-flowered; axes glabrous, smooth; bracts none or few, narrowly elliptic to narrowly lanceolate, 2-5 mm; pedicels ca. 1.5 mm. Ovary obovoid, ca. 0.5 mm, densely hispidulous with undeveloped trichomes. Corolla white or pale green, rotate, 1.5-2 mm in diam., glabrous; lobes 4, triangular, acute. Mericarps ellipsoid, 1.5-2.5 mm, with dense uncinate trichomes ca. 1 mm, fruiting pedicels divaricate and elongating to 10 mm. Fl. and fr. Jul-Sep.
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