Flora of North America species comparison

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Orbexilum

Orbexilum onobrychis

leather-root, snakeroot or leather-root

French-grass
Habit Herbs, perennial, unarmed; with lignescent rhizome, tuber, or fusiform taproot. Herbs to 10 dm; with ligneous rhizome.
Stems

erect to ascending, usually gland-dotted, pubescent or glabrous.

pubescent, glabrescent.
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.

pinnately 3-foliolate;

stipules lanceolate to linear, 4–9 mm;

petiole 20–90 mm;

leaflet blades lanceolate to elliptic-lanceolate, 40–120 × 15–50 mm, surfaces adaxially sparsely glandular-punctate, sparsely pubescent.
Inflorescences

pedunculate, 5–50-flowered, terminal, spicate;

bracts present;

bracteoles absent.

cylindric, 3–20 cm.
Peduncles

5–15 cm.
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.

5–6.5 mm;

calyx 2–3 mm, eglandular or sparsely glandular-punctate, puberulent;

corolla violet to purple, banner rounded.
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.

Legumes

8–12 × 5–5.5 mm, eglandular, papillose or warty.
Seeds

1, reniform, obovate, depressed-obovate, or round-obovate.

reniform, 4–6 mm.
x

= 11.

Orbexilum

Orbexilum onobrychis
Phenology Flowering May–Jun.
Habitat Plains, along roadsides, dry, open woods, fallow pastures.
Elevation 200–500 m. (700–1600 ft.)
Distribution
from USDA
c United States; se United States; Mexico
[BONAP county map]
from FNA
IA; IL; IN; KY; MO; NC; OH; TN; VA
[WildflowerSearch map]
[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.)

Orbexilum onobrychis is apparently extirpated from South Carolina.

(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†. FNA vol. 11.
Parent taxa Fabaceae > subfam. Faboideae Fabaceae > subfam. Faboideae > Orbexilum
Sibling taxa
O. lupinellus, O. macrophyllum, O. pedunculatum, O. psoralioides, O. simplex, O. stipulatum, O. virgatum
Subordinate taxa
O. lupinellus, O. macrophyllum, O. onobrychis, O. pedunculatum, O. psoralioides, O. simplex, O. stipulatum, O. virgatum
Synonyms Rhytidomene Psoralea onobrychis, Lotodes onobrychis, O. latifolium, P. latifolia
Name authority Rafinesque: Atlantic J. 1: 145. (1832) (Nuttall) Rydberg in N. L. Britton et al.: N. Amer. Fl. 24: 5. (1919)
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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