Herbs, perennial, unarmed; with lignescent rhizome, tuber, or fusiform taproot. Stems erect to ascending, usually gland-dotted, pubescent or glabrous. Leaves alternate, unifoliolate, palmate, or odd-pinnate; stipules present, persistent or caducous; petiolate; stipels absent; leaflets 1–7, blade margins entire, surfaces glandular-punctate or eglandular, pubescent or glabrous. Inflorescences pedunculate, 5–50-flowered, terminal, spicate; bracts present; bracteoles absent. Flowers papilionaceous; calyx tubular-campanulate, lobes 5, lobes 2–3 times tube length; corolla violet, purple, or purplish blue, banner, wings, and keel well developed, keel connate apically; stamens 10, diadelphous or proximally monadelphous; anthers in 2 series, proximal dorsifixed, distal basifixed, introrse. Fruits loments, dark brown to black, subsessile, asymmetric or curved, flattened, round-obovate to obovate, 0.4–1.2 cm, indehiscent, thickly leathery, rugose or papillose, glandular-punctate or eglandular, glabrous. Seeds 1, reniform, obovate, depressed-obovate, or round-obovate. x = 11.

Distribution

c, se United States, Mexico.

Discussion

Species 11 (8 in the flora).

As treated by J. W. Grimes (1990), Orbexilum comprises closely related species confined to North America, this largely confirmed by DNA data (A. N. Egan and K. A. Crandall 2008). B. L. Turner (2008b) proposed three additional species known from Mexico [O. chiapasanum B. L. Turner, O. melanocarpum (Bentham) Rydberg, and O. oliganthum (Brandegee) B. L. Turner], bringing to 11 the number of species recognized for the genus.

Selected References

None.

Lower Taxa

Orbexilum lupinellus, Orbexilum macrophyllum, Orbexilum onobrychis, Orbexilum pedunculatum, Orbexilum psoralioides, Orbexilum simplex, Orbexilum stipulatum, Orbexilum virgatum

Key

1	Leaves unifoliolate.	Orbexilum virgatum
1	Leaves 3–7-foliolate (sometimes unifoliolate in O. simplex).	> 2
2	Leaves mostly palmately (3–)5–7-foliolate.	Orbexilum lupinellus
2	Leaves pinnately 3-foliolate (sometimes unifoliolate or palmately 5–7-foliolate in O. simplex).	> 3
3	Leaflet blades: base cordate.	Orbexilum macrophyllum
3	Leaflet blades: base not cordate.	> 4
4	Herbs eglandular; stipules narrowly oblong, 10–13 mm.	Orbexilum stipulatum
4	Herbs ± glandular-punctate, at least adaxial leaflet surfaces; stipules long-triangular, lanceolate, or linear, 3–10 mm.	> 5
5	Legumes papillose or warty.	Orbexilum onobrychis
5	Legumes rugose.	> 6
6	Flowers 8–10 mm.	Orbexilum simplex
6	Flowers 4–7 mm.	> 7
7	Bracts, calyces, and legumes markedly glandular-punctate; bracts ovate, 5–8 × 2–4 mm; Atlantic Coastal Plain.	Orbexilum psoralioides
7	Bracts, calyces, and legumes eglandular; bracts lanceolate to narrowly ovate, 5–8 × 1–2.5 mm; sc United States.	Orbexilum pedunculatum