2. Mitreola petiolata (J. F. Gmelin) Torrey & A. Gray, Fl. N. Amer. 2: 45. 1841.
度量草 du liang cao
Cynoctonum petiolatum J. F. Gmelin, Syst. Nat. ed. 13, 443. 1790; C. mitreola (Linnaeus) Britton; C. paniculatum (Wallich ex G. Don) Robinson; Mitreola inconspicua Zollinger & Moritzi; M. oldenlandioides Wallich ex A. de Candolle; M. paniculata Wallich ex G. Don; Ophiorrhiza mitreola Linnaeus; Selenocera secundiflora Zippellius ex Spanoghe.
Annuals 10--50 cm tall, glabrous except for sparsely appressed pubescence or puberulence on young leaves, inside of corolla lobes at base, and fruit. Stems erect, simple or branched at base; branches 4-angled to narrowly 4-winged; internodes 1.5--6 cm. Interpetiolar stipules ± triangular, 1--2 mm. Petiole 3--10 mm; leaf blade ovate to narrowly ovate, 4--7 X 1.5--3 cm, membranous to papery, base cuneate, apex acuminate to obtuse, lateral veins 5--7 pairs and inconspicuous. Inflorescences terminal or axillary, 6--10 cm, many-flowered; peduncle to 7 cm; bracts and bracteoles narrowly elliptic, 1--2 mm. Pedicel very short. Calyx lobes ovate to triangular, ca. 1 X 0.5 mm. Corolla white, ca. 3 mm, tube ± as long as lobes; lobes narrowly ovate, apex obtuse. Stamens inserted at or near base of corolla tube; anthers broadly ovate, apex at ± middle of corolla tube. Ovary ovoid to subglobose, smooth. Style shorter than ovary, free to base; stigma capitate. Capsules ca. 3 mm in diam., pincerlike due to incurved apical horns. Seeds ellipsoid, ca. 0.5 mm, concave on one side, smooth. Fl. May-Oct.
Sunny areas on limestone, open woodlands, forest edges, edge of trails, grassy plains, valleys; 0-900 m. Guangxi, Guizhou, Yunnan [SE Asia; S Africa, America, N Australia].