Flora of North America species comparison

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Orbexilum

leather-root, snakeroot or leather-root
Habit 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.

Orbexilum
Distribution
from USDA
c United States; se United States; Mexico
[BONAP county map]
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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Leaves unifoliolate.
O. virgatum
1. Leaves 3–7-foliolate (sometimes unifoliolate in O. simplex).
→ 2
2. Leaves mostly palmately (3–)5–7-foliolate.
O. lupinellus
2. Leaves pinnately 3-foliolate (sometimes unifoliolate or palmately 5–7-foliolate in O. simplex).
→ 3
3. Leaflet blades: base cordate.
O. macrophyllum
3. Leaflet blades: base not cordate.
→ 4
4. Herbs eglandular; stipules narrowly oblong, 10–13 mm.
O. 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.
O. onobrychis
5. Legumes rugose.
→ 6
6. Flowers 8–10 mm.
O. 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.
O. psoralioides
7. Bracts, calyces, and legumes eglandular; bracts lanceolate to narrowly ovate, 5–8 × 1–2.5 mm; sc United States.
O. pedunculatum
Source FNA vol. 11. Author: Billie L. Turner†.
Parent taxa Fabaceae > subfam. Faboideae
Subordinate taxa
O. lupinellus, O. macrophyllum, O. onobrychis, O. pedunculatum, O. psoralioides, O. simplex, O. stipulatum, O. virgatum
Synonyms Rhytidomene
Name authority Rafinesque: Atlantic J. 1: 145. (1832)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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