Commelina vaginata Linnaeus, Mant. Pl. 2: 177. 1771; Dictyospermum vaginatum (Linnaeus) D. Y. Hong.

Herbs perennial. Roots fibrous, lanate. Rhizomes elongate, with long internodes. Stems creeping or slightly robust and ascending, branched at base, usually simple distally, 15--50 cm × 1--2.2 mm, glabrous or with a line of hairs. Leaves 2 to several; leaf sheath open; leaf blade linear, 4--10(--20) cm × 4--7 mm, glabrous, margin ciliate. Flowers 1--5, in fascicles; peduncle slender, 5--10(--20) cm; sheathlike involucral bracts 1--3 on each stem, distant, striate; pedicels 1--1.5 cm, with 2 bracteoles, hirsute distally. Sepals lanceolate, ca. 3 mm, persistent. Petals blue, obovate-orbicular. Fertile stamens 2; filaments pubescent; staminodes 3 or 4; antherodes 3-sect. Capsule globose, ca. 3 mm in diam. Seeds 1 per valve, gray-black, reticulate. Fl. Aug--Sep.

Usually on sandy beaches. Guangdong, Guangxi, Hainan, N Jiangsu (Yuntai Shan) [India, Philippines, Sri Lanka, Thailand, Vietnam].