Description from Flora of China
Herbs annual. Stems 10-40 cm tall, erect-ascending, base trailing, glabrous. Leaves in whorls of 4, linear to oblanceolate, 1-2 × 2.5-3.2 cm, glabrous, abaxially sparsely glandular, base attenuate, margin entire or slightly revolute, apex obtuse. Spikes subcapitate, 1-2.7 cm × 8-9 mm; bracts purple, lanceolate, slightly longer than calyx, margin gray villous. Calyx ca. 1 × 0.8 mm, pilose, glandular, 5-sulcate. Corolla reddish, ca. 2 × as long as calyx. Stamens much exserted. Nutlets unknown.
Specimens from Yunnan do not have the slender, erect stems and slender spikes as described by C. B. Clarke for Indian plants. This may be due to local variation.
Aquatic, marshy streamsides; 900-1500 m. Yunnan [India]