Rhynchosia minima (L.) DC., least stout bean. Perennial vine, twining, not rosetted, several–stemmed at base, growing on support or trailing; shoots with only cauline leaves on flexible stems, puberulent and with scattered, subsessile glandular hairs having yellowish heads.
Stems 6–ridged, < 2 mm diameter, with 3 conspicuous ridges descending from each leaf, tough, internodes usually twisted and to 85 mm long, ≥ leaf, glandular hairs absent from ridges, nonglandular hairs downward–pointing with some longer hairs widely spaced along ridges.
Leaves helically alternate, pinnately–3–foliolate, petiolate with pulvinus, with stipules; stipules 2, attached to stem at node, acuminate, 2—3.2 mm long, green to reddish, sometimes with lateral tooth near base, puberulent, deciduous to late–deciduous; petiole pulvinus without not noticeably swollen. 1—2.5 mm long, puberulent, above pulvinus strongly 5–ridged, glandular hairs scattered in furrows; rachis with a pair of conspicuous ridges on upper side, like petiole; stipel subtending lateral leaflet 1, subtending terminal leaflet 2, linear extentions of ridges < 0.35 mm long; petiolule = pulvinus ca. 1 mm long, puberulent with glandular hairs; bladelets of leaflets obovate to ± diamond–shaped, in range to 30 × 30 mm, broadly tapered to subtruncate or roundish, entire or with 2 broad, rounded lobes above midblade, acute to obtuse at tip, conspicuously 3–veined at base each pinnately veined with principal veins raised on both surface, glandular hairs denser on lower surface.
Inflorescence raceme, axillary, open, 5—13–flowered, bracteate, puberulent with scattered, subsessile glandular hairs having yellowish heads; peduncle strongly 5–ridged, to 15 mm long; rachis ridged with a principal ridge descending from each pedicel; bractlet subtending pedicel narrowly acuminate, to 1 mm long, puberulent, early–deciduous from persistent base; pedicel arching, 0.5—0.7 mm long.
Flower bisexual, bilateral, pealike (papilionaceous), 1 mm across; nectary inconspicuous on receptacle below ovary; calyx 5–lobed from midpoint, green, puberulent with subsessile glandular hairs; tube funnel–shaped to narrowly bell–shaped, ca. 1.3 mm diameter; lobes heteromorphic, appressed, lower lobe acuminate–linear, to 2.5 mm long, lateral 2 lobes ca. 1 mm long, upper portion deeply 2–lobed, lobes 1–veined, inner (upper) surface glabrous; petals 5, clawed, in range ca. 5 mm long, the claws whitish, limbs pale orange–yellow to light orange–yellow; banner obovate to roundish, ca. 5 × 4 mm, claw blunt, < 1 mm long, limb folded over flower, with a pair of short teeth at base, outer (lower) surface with raised veins and puberulent with subsessile glandular hairs, inner (upper) surface with radiating nectar lines; wings 2, < banner, claws slender, ca. 1.2 mm long, limbs obovate, ca. 3 × 1.3 mm, with side–pointing basal lobe deltate, 0.5 mm long, whitish, glabrous; keel of 2 petals fused on lower side of limbs, = banner, glabrous, claws slender, ca. 1 mm long, whitish, limb broadly elliptic, ca. 3.5 × 1.5 mm; stamens 10, diadelphous (9 fused and 1 free), ca. 5 mm long; filament sheet 2.5—3 mm long, whitish to pale green, free portions alternating long and short, glabrous; anthers dorsifixed, dithecal, some slightly exserted, monomorphic, ± 0.35 mm long, pale orange–yellow, longitudinally dehiscent; pollen pale yellow; pistil 1, ca. 5 mm long, slightly exserted; ovary superior, ellipsoid, to 2.5 mm long, light green, short–sericeous with upward–pointing hairs, 1–chambered with 2—3 ovules attached on upper side; style cylindric, pale green aging white; stigma terminal, capitate, papillate.
Fruit pod (legume), dehiscent with valves slightly twisting (to 180°), mostly 2–seeded, low hatchet–shaped and flat but bulging at seeds, 14—21 × 2.5—4 mm, brown to dark brown, with short point at tip, short–pilose and gland–dotted with ruby red heads.
Seed plump kidney–shaped, 3.2—3.5 × 2—2.2 mm, hard, greenish to brown mottled usually black or light gray, glossy or not; hilum median.
A. C. Gibson