Centrosema
Centrosema virginianum
butterfly-pea
blue bell, butterflypea, spur butterfly pea, Virginian centro, wild blue vine
4–8 cm × 5–11 mm proximally, to 30+ cm × 1–2 mm distally.
trailing to scandent and twining, wiry, pubescent, hairs microuncinate.
1–5, to 1–3 m × 1–2 mm.
alternate, odd-pinnate;
stipules present, persistent, striate;
petiolate;
leaflets 3, blade margins entire, surfaces glabrate abaxially, uncinulate-hairy adaxially.
stipules ovate-deltate, 3–5 mm;
petioles angular, canaliculate adaxially, 1–5 cm;
stipels persistent, striate, linear, 3–5 mm;
petiolules 2 mm;
rachis 0.5–1.5 cm;
leaflet blades ovate to elliptic, ovate to lanceolate, or oblong to linear, (12–)20–65(–100) × 8–45 mm, thinly leathery, base rotund, primary lateral veins of 6–8 pairs, to 15 pairs in linear leaflets, veins with uncinulate hairs, apex broadly acute.
1 or 2(–4)-flowered, axillary, pseudoracemes;
bracts present, persistent;
bracteoles deciduous in fruit, appressed to calyx, often obscuring calyx tube and distal and lateral lobes.
1(or 2) per node, 1–3 cm;
bracts striate, concave around pedicel, oval-ovate, 4–6 mm;
bracteoles striate, lanceolate-ovate, 6–8 × 3–5 mm, surfaces with uncinulate hairs;
rachis subflexuous, 1–2(–3) cm, strigose.
paired, borne laterally at peduncle apex, spirally twisted to invert flowers.
5–8 mm, 7–11 mm in fruit, thinly pilose.
papilionaceous, resupinate, showy;
calyx campanulate, lobes 5, equal to or longer than tube, 2 abaxial lobes connate, adaxial lobe conspicuous, often extending between bracteoles;
corolla lavender, pinkish lavender, bluish violet, or purple, 20–35(–40) mm, banner conduplicate, spurred or gibbous, distal to claw, obovate-orbiculate, emarginate, with medial white stripe on adaxial surface;
wings slightly adherent to keel, falcate-obovate, with auricles distal to claw, subequal to keel;
keel incurved, adaxial margin broadly U-shaped;
stamens 10, diadelphous, distinct apically;
anthers dorsifixed or basifixed, uniform;
style strongly incurved, broadly U-shaped, flattened, base persistent as beak in fruit, ± dilated apically, barbellate near apex.
calyx tube 3–4 × 4–6 mm, lobes subequal, abaxial ones 4–7 mm, lateral ones 5–8 mm, adaxial ones 6–10 mm, hairs uncinulate;
corolla lavender to bluish violet or purple;
banner 25–35(–40) mm, claw 2–4 mm, spur 1–2 mm;
wings 14–19 × 5–9 mm, claw 5–7 mm;
keel 16–20 × 7–10 mm, claw 3–5 mm;
staminal tube 19–25 mm;
apical distinct filaments 1–3 mm;
ovary 12–15 mm;
style 20–27 mm, apex dilated 9–12 × 1 mm.
legumes, sessile, green, straight, compressed, flat with raised rib near margin, linear, 3–6 mm wide, dehiscent by valves breaking from replum and spirally twisting to expel seeds, glabrate.
dehiscence causing valve to twist (1–)3–5 turns, (60–)80–110 × 3–5 mm;
beak 9–17 mm.
8–18, reniform, smooth.
14–18, dark brown, 3–4 × 4–6 × 1 mm.
= 10.
= 14, 18, 22.
Centrosema
Centrosema virginianum
Species ca. 35 (2 in the flora).
Centrosema is a woody genus of shrubs, lianas, and suffrutescent herbs with scandent aerial stems. It has become an important agronomic crop in the past several decades, with germplasm being spread throughout the paleotropics. Centrosema molle Martius ex Bentham (reported as C. pubescens Bentham), C. plumieri (Turpin ex Persoon) Bentham, and C. sagittatum (Humboldt & Bonpland ex Willdenow) Brandegee are reported in references and on the internet as native to Florida. All vouchers are from cultivated specimens; those taxa are excluded here. A specimen of C. sagittatum collected by Erdman West (FLAS, 61296, “Alachua Co. seeds collected winter 1949–1950, collected in hammock near Newman’s Lake on Oct 1950”) has been cited as documentation for being native in Florida; the plant was introduced from Mexico and grown in a cultivated legume plot.
Centrosema and Clitoria are unique legumes with relatively large, resupinate flowers. Both genera have microuncinate hairs (viewed at 20–30×) on their vegetative and reproductive structures. Both have aerial stems arising seasonally from a subterranean xylopodium that often is not collected. The proximal portion of the xylopodium is thickened, lignose, and scarred with bases of prior aerial stems. Extending from this is an elongated, narrow, distal portion that extends laterally away from the aerial plant and deeper into the ground, easily breaking apart as one attempts to collect it, leaving much in the ground. Historically, the similar appearances of Centrosema and Clitoria have resulted in misidentifications. Clitoria is distinguished easily by the funnelform calyx, geniculate styles, U-shaped corollas, wings extending beyond the keel, and, in the flora area, turgid fruits that are depressed between the seeds, or flat and ecostate.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Historically, Centrosema virginianum has been misidentified as Clitoria mariana by collectors in the United States. The latter species is distinguished easily by the non-scandent, erect stems, funnelform calyces with lobes broader and shorter than tubes, spurless banners, wings longer than keel petals, presence of cleistogamy, and turgid, ecostate fruits depressed slightly between the seeds.
Two varieties of Centrosema virginianum have been described based upon leaflet width. Specimens with narrow, linear leaves (var. angustifolium) found in the southern coastal areas appear distinct from those found inland with broader and shorter leaves (var. ellipticum, var. virginianum). Examined specimens exhibit a gradation in leaflet width and length, from multiple collections within a population, to variation within one plant, bearing shorter and broader leaves at proximal nodes and narrower and longer leaves at distal nodes. Varieties are not recognized here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Calyx lobes unequal; inflorescence bracteoles 8–10 mm; stipules and stipels 1–2 mm; pedicels 10–14 mm in fruit; legumes 5–6 mm wide. | C. arenicola |
1. Calyx lobes subequal; inflorescence bracteoles 6–8 mm; stipules and stipels 3–5 mm; pedicels 7–11 mm in fruit; legumes 3–5 mm wide. | C. virginianum |
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