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| 1 Inflorescence nearly sessile, of 1-4 flowers clustered in the leaf axil; [alien species]. |
| ..2 Leaves with 2-6 leaflets, succulent; leaflets 3-7 cm long; legume with pectinate sutures |
| ..2 Leaves with 4-20 leaflets, not succulent; leaflets 0.3-3.5 cm long; legume not pectinate (except V. lutea). |
| ....3 Corolla 5-6 mm long; leaves with 4-6 (-8) leaflets |
| ....3 Corolla 10-30 mm long; leaflets 6-16 (-20). |
| ......4 Calyx lobes conspicuously unequal; legumes pilose with pustulate-based hairs |
| ......4 Calyx lobes more or less equal; legumes glabrous at maturity, or very finely pubescent with non-pustulate-based hairs. |
........5 Calyx lobes all shorter than the calyx tube; corolla yellow, often streaked with purple, 25-30 mm long |
| ........5 Calyx lobes (at least the longer) about as long as the calyx tube; corolla pink, purple, lavender, white, or creamy yellow, 10-25 (-30) mm long. |
| ..........6 Standard pubescent dorsally; corolla 15-25 (-30) mm long, creamy yellow to purple; legume pubescent, with a basal stipe |
| ..........6 Standard glabrous; corolla 10-25 (-30) mm long, pink, purple, lavender, or whitish; legume glabrous, sessile. |
| ............ 7 Calyx 7-11 (-12) mm long; corolla pink-purple to whitish, 10-18 mm long; leaflets 4-10× as long as wide |
| ............ 7 Calyx 10-15 mm long; corolla generally pink-purple, 18-25 (-30) mm long; leaflets 2-5 (-7)× as long as wide |
| 1 Inflorescence pedunculate, of 2-many flowers along a well-developed raceme; [alien and native species]. |
| ............ ..8 Peduncles 1-10 mm long; raceme axis 2-10 mm long, with 2-7 (-10) flowers. |
| ............ ....9 Plant a robust annual, 10-20 dm tall; tendrils absent; leaves with (2-) 4-6 leaflets; leaflets 5-10 cm long; corolla 20-30 mm long |
| ............ ....9 Plant a trailing perennial, 3-10 dm tall; tendrils present; leaves with 8-16 leaflets; leaflets 2-3.5 cm long; corolla 10-15 mm long |
| ............ ..8 Peduncles usually > 10 mm long; raceme axis usually >10 mm long, with (1-) 2-many flowers. |
| ............ ......10 Corolla 10-25 mm long. |
| ............ ........11 Stipules dimorphic, one of each pair entire, the other palmately lacerate; flowers 1 (-2) per inflorescence |
| ............ ........11 Stipules of a pair alike; flowers 1-numerous per inflorescence. |
| ............ ..........12 Flowers 15-22 (-25) mm long; legumes with a basal stipe 2-5 mm long; leaves with 8-16 leaflets |
| ............ ..........12 Flowers 8-16 (-18) mm long; legumes with a basal stipe 1-3 mm long; leaves with 8-22 leaflets. |
| ............ ............ 13 Calyx swollen on one side; plant an annual; inflorescence secund. |
| ............ ............ ..14 Plant glabrate or with pubescence of incurved or loosely appressed hairs < 1 mm long; lower calyx lobe lanceolate to linear-lanceolate, 1-2 (-3) mm long; leaflets 2-4 mm wide |
| ............ ............ ..14 Plant conspicuously villous, the hairs spreading and 1-2 mm long; lower calyx lobe acicular or weak, (2-) 3-4 mm long; leaflets 3-6 mm wide |
| ............ ............ 13 Calyx not swollen on one side; plant a rhizomatous perennial; inflorescence not secund. |
| ............ ............ ....15 Flowers white to lavender, the keel spotted; legumes 4-5 mm wide; inflorescence not secund |
| ............ ............ ....15 Flowers blue-violet or purple; legumes 6-8 mm wide; inflorescence generally secund |
| ............ ......10 Corolla 2.5-8 (-10) mm long. |
| ............ ............ ......16 Plant a rhizomatous perennial. |
| ............ ............ ........17 Leaves with 2-4 (-6) leaflets; [plants of s. SC southward, native, of the Coastal Plain]. |
| ............ ............ ..........18 Legumes 2.5-3.0 cm long; leaflets 1.5-4.5 cm long, oblong to linear, 8-20× as long as wide |
| ............ ............ ..........18 Legumes 0.8-1.5 cm long; leaflets 1-1.5 cm long, usually elliptic, 2-4 (-10)× as long as wide |
| ............ ............ ........17 Leaves with 10-25 leaflets; [plants collectively widespread in our area, native or alien]. |
| ............ ............ ............ 19 Flowers white to lavender, the keel spotted; legumes 4-5 mm wide; inflorescence not secund |
| ............ ............ ............ 19 Flowers blue-violet or purple; legumes 6-8 mm wide; inflorescence generally secund |
| ............ ............ ......16 Plant an annual. |
| ............ ............ ............ ..20 Legume symmetrically rounded at the apex; inflorescence with 1-2 (-4) flowers |
| ............ ............ ............ ..20 Legume asymmetrically acute at the apex; inflorescence with 1-15 flowers. |
| ............ ............ ............ ....21 Leaves with 2-4 leaflets; legume glabrous to inconspicuously puberulent |
| ............ ............ ............ ....21 Leaves with (8-) 10-16 leaflets; legume glabrous or finely hirsute. |
| ............ ............ ............ ......22 Legume finely hirsute; calyx 2-2.5 mm long; corolla 2.5-4.5 mm long |
| ............ ............ ............ ......22 Legume glabrous; calyx 2.8-3.7 mm long; corolla 4.5-8 mm long. |
| ............ ............ ............ ........23 Flowers opening before the peduncle elongates; young fruits often present and visible when flowers open; style 0.6-0.8 mm long; leaflets generally 11-15. |
| ............ ............ ............ ..........24 Flowers 1-6 per inflorescence; legumes generally < 3 cm long; leaflets 2.5-7× as long as wide; [sw. MO west to w. OK, south to e. and wc. TX] |
| ............ ............ ............ ..........24 Flowers 1-2 per inflorescence; legumes generally > 3 cm long; leaflets 2-3× as long as wide; [ne. AR and se. OK south to w. MS and s. LA] |
| ............ ............ ............ ........23 Flowers opening after the peduncle elongates; young fruits not present when flowers open; style (0.6-) 0.8-1.4 (-1.7) mm long; leaflets (5-) 7-10 (-13). |
| ............ ............ ............ ............ 25 Style 1.0-1.5 (-1.7) mm long; calyx tube (1.3-) 1.7-2.0 (-2.5) mm long; {OK, TX westwards]. |
| ............ ............ ............ ............ ..26 Flowers 1-15 per inflorescence; peduncle (when flowers open) 1.5 cm long, about as long as the subtending leaf; [widespread in s. OK and e., nc., and c. TX, s. NM, and Mexico] |
| ............ ............ ............ ............ ..26 Flowers 1-5 per inflorescence; peduncle (when flowers open) 1-5 cm long, about one third as long as the subtending leaf; [s. TX westwards] |
| ............ ............ ............ ............ 25 Style (0.6-) 0.8-1.2 (-1.3) mm long; calyx tube (1.1-) 1.4-1.8 (-2.2) mm long; [e. GA west through FL, AL, MS, and LA to AR and TX]. |
| ............ ............ ............ ............ ....27 Flowers (2-) 5-9 (or more) per inflorescence; [e. GA, FL Panhandle, s. AL, s. MS, AR and nc. TX south to s. LA and se. TX] |
| ............ ............ ............ ............ ....27 Flowers generally 3 per inflorescence, one terminal, the other 2 paired below; [se. TX southwest to s. TX, and as a waif east to Panhandle FL] |