Keel of the corolla with the included stamens and style elongated, strongly incurved, not spirally coiled. Pod linear, terete or flattish, straight or nearly so. Seeds quadrate or oblong with truncate ends, mealy-pubescent or glabrate; hilum linear. Flowers few, sessile and capitate clustered on the mostly long peduncles. Otherwise as Phaseolus.--Stems prostrate or climbing, more or less retrorsely hairy. Stipules and bracts striate. (Name from στροφή, _a turning_, and στῦλος, _a style_.) 1. S. angulòsa, Ell. _Annual_; stems branched, 1--6° long; leaflets ovate to oblong-ovate (rarely linear-oblong), _with a more or less prominent rounded lobe toward the base (the terminal 2-lobed)_, or some or all often entire, about 1´ (6--20´´) long; corolla greenish-white and purplish; pod terete, 2--3´ long by 3´´ wide, 4--8-seeded, nearly glabrous; _seeds oblong, about 3´´ long_, usually very pubescent. (Phaseolus diversifolius, _Pers._ P. helvolus, _L._)--Sandy shores and river-banks; coast of Mass. and southward, along the Great Lakes to Minn., and south to Kan. and Tex. Var. Missouriénsis, Watson in herb. Climbing high (10--30°); leaves often 3´ long, rhombic-ovate, rarely at all lobed; seeds 3--4´´ long.--River-bottoms near Independence, Mo.; nearly two months later. (_F. Bush._) 2. S. pedunculàris, Ell. Stems _more slender_, from a _perennial_ rootstock, 2--4° long; leaflets ovate to oblong-linear, _rarely at all lobed_, 1´ long or less; pod 1½--2´ long and _scarcely 2´´ wide_; seeds _much smaller_, 1½--2´´ long, short-oblong to quadrate. (Phaseolus helvolus, _Man._, etc., not _L._)--Sandy ground, Long Island and N. J. to Fla., west to S. Ind., Ky., and La. 3. S. pauciflòrus, Watson in herb. _Annual_, slender, low-climbing, pubescent; leaflets oblong-lanceolate or ovate-oblong to linear, not lobed, 1´ long; pod pubescent, 1´ long, flattish; seeds as in the last, very finely mealy, soon glabrate. (Phaseolus pauciflorus, _Benth._)--River-banks, Ind. to Minn., south to Miss. and Tex. 35. CENTROSÈMA, DC. SPURRED BUTTERFLY-PEA. Calyx short, 5-cleft. Corolla, etc., much as in Clitoria, but the spreading standard with a spur-shaped projection on the back near the base; keel broad. Style bearded at the apex around the terminal stigma. Pod long and linear, flat, pointed with the awl-shaped style, many-seeded, thickened at the edges, the valves marked with a raised line on each side next the margin.--Twining perennials, with 3-foliolate stipellate leaves, and large showy flowers. Stipules, bracts, and bractlets striate, the latter longer than the calyx. (Name from κέντρον, _a spur_, and σήμα, _a standard_.) 1. C. Virginiànum, Benth. Rather rough with minute hairs; leaflets varying from oblong-ovate to lanceolate and linear, very veiny, shining; peduncles 1--4-flowered; calyx-teeth linear-awl-shaped; corolla violet, 1´ long; pods straight, 4--5´ long.--Sandy woods, Md. to Fla. and Ark. (Trop. Am.) 36. CLITÒRIA, L. BUTTERFLY-PEA.