Plants 15-50 cm tall. Stem erect, light green, firm, obscurely ribbed, covered with ramified hairs when young, branched from base; lowest branches often opposite or whorled, spreading; upper branches opposite, obliquely spreading. Leaves sessile, lanceolate to linear, 1.3-7 cm × 1-10 mm, base attenuate, apex acute; longitudinal veins 3-9, prominent. Spikes axillary, sessile, dense, ovoid or ellipsoid; bracts broadly ovate, reflexed in fruit, abaxially hairy, apex abruptly acute, mucronate. Perianth segments 1-3, membranous. Stamens 2 or 3; filaments subulate, pellucid; anthers ovoid. Utricle ovoid or ellipsoid, compressed, slightly convex abaxially, hairy when young, slightly wing-margined distally; beak parted into 2 slightly recurved, linear, compressed beaks, each usually with a subapical, small, flattened tooth. Seed subglobose, glabrous, sometimes speckled with light brown. Fl. and fr. Aug-Oct.