二萼丰花草 er e feng hua cao

Borreria exilis L. O. Williams, Phytologia 28: 227. 1974, based on B. gracilis L. O. Williams, Phytologia 26: 487. 1973, not Scheele (1844), nor Spermacoce gracilis Ruiz & Pavon (1798); B. repens Candolle; S. decandollei Deb & R. M. Dutta, nom. illeg. superfl.; S. mauritiana Gideon; S. repens (Candolle) Fosberg & D. A. Powell (1980), not Willdenow ex Chamisso & Schlechtendal (1828), nor Sessé & Mociño (1893), nor Larrañaga (1923).

Herbs, annual to perhaps perennial, slender, creeping to weakly ascending, to 30 cm tall; stems 4-angled, puberulent to glabrescent, angles winged, wings 0.1-0.5 mm wide, ciliate or ciliolate. Leaves subsessile to shortly petiolate; petiole to 1.5 mm, puberulent to glabrescent; blade drying membranous, ovate or elliptic-oblong, 0.7-30 × 4-15 mm, sparsely puberulent to glabrous throughout or pilose to hispid along midrib abaxially, base obtuse to cuneate, apex acute to obtuse; secondary veins 2 or 3 pairs; stipules pilosulous or hirtellous to glabrescent, sheath 0.5-1 mm, with 5-10 bristles 0.5-2 mm, often glandular. Inflorescences terminal and in uppermost leaf axils, 3-6 mm in diam., several to many flowered; bracts numerous, filiform, 0.5-1.5 mm. Calyx hirtellous to glabrescent; hypanthium portion obovoid, ca. 0.3 mm; lobes 2, linear-lanceolate to triangular, 0.4-0.9 mm. Corolla white, rotate to shortly tubular, 0.5-0.6 mm, outside glabrous, bearded in throat; lobes spatulate triangular, ± as long as tube. Capsules ellipsoid, weakly to strongly flattened at right angles to septum, 1-1.1 × 0.8-1 mm, glabrescent, membranous and sometimes somewhat hyaline, septicidal from apex then both valves loculicidal through septum or sometimes fragmenting; seeds brownish yellow, ellipsoid, ca. 0.8 × 0.4 mm, obtuse at both ends, shiny, surface apparently with numerous fine horizontal striations or ridges (at 10×; but actually with minute transverse pits, visible at 40×). Fl. and fr. almost year-round.

Naturalized in disturbed humid sites at low elevations. Hainan, Hong Kong, Taiwan [apparently native to the Neotropics but exact origin unknown; India, Indonesia, Nepal, Sri Lanka, Vietnam; Africa, Antilles, Australia, Central America, Indian Ocean islands (Mauritius), North America (Mexico), Pacific islands, N South America].

The seeds of this species were illustrated in detail by Chaw and Sivarajan (Bot. Bull. Acad. Sin., n.s., 30: 20, f. 28-30. 1989, as Spermacoce mauritiana). The taxonomy and circumscription of this adventive species here follows Burger and Taylor (Fieldiana, Bot., n.s., 33: 316. 1993). The illustration presented by Deb and Dutta (J. Econ. Taxon. Bot. 5(5): 1045, f. 2. 1984, as S. decandollei) seems to be based on a mixed collection of S. exilis and S. prostrata according to the circumscription of these species here. Both S. exilis and S. prostrata were formerly included in a broadly circumscribed, morphologically heterogeneous "Spermacoce ocymoides Burm. f." Several authors have concluded that this last name applies to a species found only in SE Asia and was incorrectly applied to American and adventive plants (Dessein, Syst. Stud. Spermacoceae (Ph.D. Diss.), University of Leuven, Belgium, 1-403. 2003, and references cited there); presumably the species treated by Bakhuizen f. in the Fl. Java is "true" S. ocymoides.

The description of Spermacoce exilis here includes observations from specimens from outside China; this species has probably been introduced to China more than once, thus it seems useful to include the variation found in adjacent regions that may yet be found in China.