Centrosema
butterfly-pea
trailing to scandent and twining, wiry, pubescent, hairs microuncinate.
alternate, odd-pinnate;
stipules present, persistent, striate;
petiolate;
leaflets 3, blade margins entire, surfaces glabrate abaxially, uncinulate-hairy adaxially.
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.
paired, borne laterally at peduncle apex, spirally twisted to invert flowers.
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.
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.
8–18, reniform, smooth.
= 10.
Centrosema
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.)
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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