Description from Flora of China
Annuals, to 38 cm tall. Stems erect, basally terete, apically branched and ribbed, with short crisp hairs. Leaves opposite or upper subalternate; leaf blade linear, to 5 cm X 1.5 mm, adaxially hispidulous, margin revolute; midrib abaxially raised. Racemes sparsely flowered, in a large panicle; lower bracts longer than flowers, upper ones shorter. Pedicel 1.5-2 mm, pubescent. Bracteoles 2, near base of calyx. Calyx ca. 1.5 mm, 10-veined; lobes narrowly triangular, subequal, outside hispidulous, inside glabrous, apex acute; fruiting calyx inflated to 3.5 X 5 mm, shallowly campanulate, outside hispidulous, sinuses rounded. Corolla purplish, ca. 1 cm; tube ca. 7 mm; lobes obovate, subequal. Ovary and style hispidulous; stigmas 2. Capsule 5-6 mm, much longer than persistent calyx, hispidulous, apex deeply concave, to 2/5 of capsule length. Seed dark brown, irregularly oblong. Fl. and fr. Sep.
* Moist grassland; 100-400 m. Hunan, Jiangsu, Zhejiang.