7. Commelina undulata R. Brown, Prodr. 270. 1810.
波缘鸭跖草 bo yuan ya zhi cao
Commelina obliqua Buchanan-Hamilton ex D. Don var. mathewii C. B. Clarke; C. paludosa Blume var. mathewii (C. B. Clarke) R. S. Rao & Kammathy; C. kurzii C. B. Clarke; C. striata Edgeworth.
Herbs perennial. Stems erect or ascending, diffuse, numerous branched, to 60 cm, glabrous. Leaves sessile; leaf sheath usually ciliate; leaf blade lanceolate, 6--9 × 1.2--2.8 cm, glabrous or ± hirsute on both surfaces. Involucral bracts 2--4, in fascicles at apex of branches and opposite smaller leaves, sessile, funnelform, 2--2.5 cm, glabrous or ± hirsute, proximal margins partly connate (2--3 mm free), apex retrorsely falcate-acuminate. Proximal branch of cincinni often abortive, sometimes with ca. 2 cm long peduncle but without flowers, distal branch with peduncle to 1 cm and with several flowers; pedicels twisting. Sepals 3.5--4 mm, membranous. Petals pinkish blue, to 1 cm. Capsule subglobose, 3--4 mm, 2- or 3-valved, sometimes only 1 valve containing seed and dehiscent; posterior valve indehiscent. Seeds 1 per valve, brown-black, oblong, ca. 4 mm, flat on 1 surface. Fl. and fr. Jul--Dec.
Humid mountain slopes. Guangdong, S Sichuan (Leibo Xian), Taiwan, E and S Yunnan [India, Indonesia, Philippines; tropical Oceania].
Commelina undulata is common in tropical Oceania, but scattered in Asia. It varies widely, with plants erect or diffuse, glabrous or hairy, and capsule (1 or)2- or 3-valved. The species is characterized by having apically falcate-acuminate involucral bracts only partly connate at the proximal margins, arising opposite the fascicled smaller leaves, and therefore resembling compound heads.