Flora of North America species comparison

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Vigna

cowpea
Stems

spreading, climbing, twining, or erect, striate, glabrous or pubescent, hairs not uncinate.
Leaves

alternate, odd-pinnate;

stipules present, persistent, slightly auriculate, distinctly peltate, or conspicuously retrorse;

petiolate;

leaflets 3, stipels present, blades 1.5–16 cm, membranous or firm, margins usually entire or shallowly deeply incised, surfaces glabrous or pubescent.
Inflorescences

2–30-flowered, axillary, pseudoracemes, with swollen floral nodes, glandular, 2 flowers per node, clustered distally;

bracts present, primary nodal bracts deciduous, entire;

bracteoles minute or deciduous, shorter or longer than calyx.
Pedicels

erect, arcuate to reflexed near pod.
Flowers

papilionaceous;

calyx campanulate, 2–6 mm, lobes 4, shorter to longer than tube, adaxial lobes usually ± connate;

corolla greenish yellow to golden yellow, purple, or white, sometimes with reddish veins, 7–30 mm;

banner symmetric or asymmetric, glabrous, often with appendages on central, inner face, slightly to strongly thickened at point where reflexed, apex emarginate;

wings subequal to banner and keel;

keel apically expanded, sometimes appendaged;

stamens 10, diadelphous, vexillary filament thickened at base;

pollen triporate;

anthers dorsifixed;

ovary with nectary disc at base, linear;

style incurved, with distal brush, usually extended beyond stigma into conic or slender tip;

stigma lateral.
Fruits

legumes, ascending, spreading, or pendulous, stipitate, usually linear to falcate, valves membranous or paper, dehiscent, resupinate by twisting of pedicel, glabrous.
Seeds

1–25, globular to oblong, cylindric, or reniform;

hilum concave or protruding; mostly with white rim aril;

seedlings hypogeal or epigeal.
Vines

, annual or perennial, herbaceous [woody], 1–3 m;

roots tuberous or fibrous.
x

= 10, 11.

Vigna
Distribution
from USDA
Asia; Africa [Introduced in North America; introduced also in Mexico, West Indies, Central America, South America]
[BONAP county map]
Discussion

Species ca. 60 (5 in the flora).

Vigna species occur mostly in the tropics and warmer temperate regions of Asia and Africa; fewer than ten occur in the New World (D. Isely 1998; N. Tomooka et al. 2002; N. Maxted et al. 2004; A. Delgado-Salinas et al. 2011). Seven species have been cultivated in the flora area: V. aconitifolia (Jacquin) Maréchal (moth bean), V. angularis, V. hosei, V. mungo (Linnaeus) Hepper (mung bean), V. radiata, V. umbellata (Thunberg) Ohwi & H. Ohashi (rice bean), and V. unguiculata (R. L. Fery 2002). Only four have become locally naturalized, in addition to the widely distributed V. luteola.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Stipules slightly auriculate or unequally lobed at base; corollas yellow, keel petals incurved or broadly curved, distally expanded or vertically incurved; legumes pendulous.
→ 2
2. Corollas 7–10 mm; legumes 2–3 cm; seeds 1–4.
V. hosei
2. Corollas 15–20 mm; legumes 4–7 cm; seeds 5–12.
V. luteola
1. Stipules with narrower appendage at base or distinctly peltate; corollas white or purple (rarely yellowish), grayish yellow, or golden yellow, keel petals slightly twisted right, incurved through 1 circle, or apex incurved nearly 1/2 circle; legumes spreading or pendulous.
→ 3
3. Stipules with narrow appendage at base; corollas usually white or purple, rarely yellowish, 25–30 mm; bracteoles equal to calyx tubes; keel without lateral appendage; style short- beaked, lobelike appendage at stigma short; legumes 10–30 cm; seeds 18–25.
V. unguiculata
3. Stipules distinctly peltate; corollas grayish yellow to golden yellow, 10–15 mm; bracteoles longer than calyx tubes; keel with lateral keel-pocket or hornlike appendage supporting left wing petal; style elongate-beaked, lobelike appendage extending beyond stigma into slender tip; legumes 4–11 cm; seeds 5–15.
→ 4
4. Stipules widely ovate; corollas grayish yellow; legumes with hispid hairs, yellowish brown becoming black; seeds globose to oblong or shortly cylindric, green or yellow- brown, rim-aril not raised.
V. radiata
4. Stipules lanceolate; corollas golden yellow; legumes sparsely pilose, glabrescent, brown; seeds oblong to cylindric, grayish brown or red, rim-aril raised.
V. angularis
Source FNA vol. 11. Author: Alfonso Delgado-Salinas.
Parent taxa Fabaceae > subfam. Faboideae
Subordinate taxa
V. angularis, V. hosei, V. luteola, V. radiata, V. unguiculata
Synonyms Azukia
Name authority Savi: Nuovo Giorn. Lett. 8: 113. (1824) — name conserved
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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