Rhynchosia americana (Mill.) Metz

  • Authority

    Grear, John W. 1978. A revision of the New World species of Rhynchosia (Leguminosae-Faboideae). Mem. New York Bot. Gard. 31 (1): 1-168.

  • Family

    Fabaceae

  • Scientific Name

    Rhynchosia americana (Mill.) Metz

  • Description

    Species Description - Herb, from thick, woody rootstock, to 100 cm, the stems procumbent, trailing or twining, several to numerous, branching, angled, villous or villosulose, the hairs silvery and usually spreading. Stipules ovate-lanceolate, acuminate, persistent, 2-5 mm long, 1-2.5 mm wide. Petioles densely villosulose, (l-)2-3(-5) cm. Leaflet 1 (the uppermost rarely 3), coriaceous, suborbicular to reniform, broadly rounded (rarely obtuse), base cordate, 1.5-3(-4) cm long, 2-5(-6) cm wide, rugose and finely strigulose above, gland-dotted and villosulose beneath, especially along the veins, stipels lacking. Inflorescences unbranched, few-flowered (2-8), usually not exceeding the leaves, 1.5-4(-5) cm, flowers loosely to more commonly closely clustered at end of peduncle, which is 0.5-2.5 cm, pedicels 2-5 mm. Bracts linear-lanceolate, acuminate, caducous, 2-3 mm long, 1-1.5 mm wide. Calyx equalling or exceeding the corolla, villosulose, 7-13 mm, tube 1.5-2 mm, lobes lanceolate, acute to acuminate, 6-9(-10) mm, vexillar sinus 2-4 mm. Corolla yellow, often tinged brown, 6-10 mm. Standard obovate, emarginate, puberulous, 8.5-10 mm long, 6.5-7.5 mm wide, auricles 1 mm, claw 1-1.5 mm. Wings narrowly oblong, glabrous, 6.5-7.5 mm long. 2-2.5 mm wide, claw 2 mm. Keel blades falcate, glabrous, 8-9 mm long, 3-3.5 mm wide, claw 2-2.5 mm. Stamens 7.5-8.5 mm. Fruits oblong-ovate, compressed, villosulose, 1-1.5 cm long, 5-8 mm wide, beak 1-1.5 mm. Seeds suborbicular, compressed, brown, black or mottled, 3-4 mm long, 3-3.5 mm wide, hilum ovate, 0.5-1 mm, strophiole lobes cuneate.

  • Discussion

    Lathyrus americana Houstoun ex Miller, Gard. Diet. ed. 8, No. 19. 1768. Dolicholus americanus (Miller) Vail, Bull. Torrey Club 26: 111. 1899. Rhynchosia menispermoidea de Candolle, Mem. Legum. 364, t. 55. 1825. Type: MEXICO. “ . . . d’Acapulco ou elle a ete decouverte par Née ...” (holotype, G-DC, not seen; phototypes, MO!, NY!, TEX!, US!). Glycine menispermoides (de Candolle) Sprengel, Syst. Veg. 4, II: 270. 1827. Phaseolus menispermoidea (de Candolle) Eaton & Wright, N. Am. Bot. 352. 1840. Type. MEXICO. Veracruz. Houstoun sn, w/o date (holotype, BM!; phototype, NY!). As indicated in the key, R. americana is most like R. michauxii and the relationship between the two is close, but the latter species only grows in Florida, well out of the range of R. americana. I have seen one collection (Godfrey 50399) of what appears to be R. americana from Southport in Brunswick County, North Carolina, collected in 1950 and reported as an abundant weed. This should be regarded as a stray introduction.

  • Distribution

    Distribution. Southeastern Texas; eastern and western Mexico, near the coasts (Fig. 4). Occurring on sandy soil in prairies, pastures and oak woodlands, and also along roadsides or in sand dunes near sea shores; at low elevations.

    United States of America North America| Mexico North America|