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Key to Centrosema

Fabaceae

Centrosema

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1 Leaves 1-foliolate; petioles conspicuously winged
1 Leaves 3-7-foliolate; petioles not winged.
  2 Leaflets 5-7-foliolate; [rare exotic]
  2 Leaflets 3-foliolate; [natives, collectively common and widespread].
    3 Calyx tube (of chasmogamous flowers) 4-5 mm long, shorter than or about as long as the lobes; bracteoles 5-12 mm long, partly enclosing the calyx tube; legume 6-12.5 cm long, 3-6 mm broad; standard 2.5-3.5 cm long, spurred near the base.
      4 Lower calyx lobe 5-8 mm long, subulate to lanceolate; upper (bifurcate) calyx lobe 3-4 mm long; bracteoles 5-7 mm long; stems to 3 m long; [of n. FL southward]
      4 Lower calyx lobe 8-11 mm long, subulate; upper (bifurcate) calyx lobe 7-8 mm long; bracteoles 8-12 mm long; stems to 1.5 m long; [widespread in our area].
        5 Terminal leaflets > 8× as long as wide; main lateral veins of terminal leaflets 10-20+; [s. GA, s. AL, south to s. FL]
        5 Terminal leaflets < 6× as long as wide; main lateral veins of terminal leaflets 5-7; [widespread in our area, south to s. FL]
    3 Calyx tube (of chasmogamous flowers) 7-13 mm long, much longer than the lobes; bracteoles 3-7 mm long, not enclosing the calyx tube; legume 3-5 cm long, 5-7 mm broad; standard 4-6 cm long, not spurred.
          6 Leaflets 3.0-4.5× as long as wide, obtuse at the tip; calyx tube of chasmogamous flowers 7-10 mm long, usually purplish; legume on a stipe 15-20 mm long, well exserted from the calyx; erect or ascending herb, 2-6 dm tall; [peninsular FL]
          6 Leaflets 1.7-3.5× as long as wide, slightly acute at the tip; calyx tube of chasmogamous flowers 10-13 mm long, green; legume on a stipe 10-15 mm long, included or slightly exserted from the calyx; ascending herb, becoming a sprawling, trailing, or twining herbaceous vine; [collectively widespread in our area].
             7 Leaves glabrescent beneath, at maturity the hairs confined or very nearly so to the major veins; [widespread in our area]
             7 Leaves moderately to densely pubescent beneath, the hairs erect and pilose to suberect and sericeous, at maturity occurring across the leaf surface; [endemic to FL peninsula]
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Key to Fabaceae, Key I: herbaceous legumes with all leaves unifoliolate or leaflets absent [subfamily Faboideae]

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1 Tendrils present on plant; leaves modified into tendrils (leaflike structures present clearly interpretable as stipules); [tribe Fabeae].
  2 Legume 4-7 mm wide; corolla 10-13 mm long
  2 Legume 12-20 mm wide; corolla 18-25 mm long
1 Tendrils absent; leaves or stipules present on plant and interpretable as leaves with 1 leaflet.
    3 Leaflet blades roundish, 0.6-1.5× as long as wide.
      4 Leaves with a well-developed petiole, > 0.5 cm long.
      4 Leaves sessile, subsessile, or perfoliate.
          6 Corolla bright or creamy yellow; stamens separate; leaves all 1-foliolate; leaflet blades perfoliate or sessile; [tribe Thermopsideae]
          6 Corolla violet to blue (drying pale); stamens diadelphous; leaves 1-foliolate and with some leaves 3-foliolate or 2-foliolate; leaflet blades cuneate, subsessile; [tribe Psoraleeae]
    3 Leaflet blades elongate, 1.5-15× as long as wide.
             7 Leaves basally disposed.
               8 Leaflet blades elliptic, widest near the midpoint of the blade; flowers pink, rose, or purplish; legume straight; [native of the Coastal Plain, se. NC south to s. FL, west to e. LA]; [tribe Genisteae]
               8 Leaflet blades oblanceolate, widest well past the midpoint of the blade; flowers yellow; legume coiled; [rare waif]; [tribe Loteae]
             7 Leaves all or primarily cauline.
                 9 Leaves long-petioled, the petiole > 2 cm long.
                   10 Petiole winged its entire length; leaflet blade 2-4× as long as wide, sagittate at the base; foliage not glandular; [tribe Phaseoleae]
                   10 Petiole not winged; leaflet blade 8-15× as long as wide, cuneate at the base; foliage glandular-punctate; [tribe Psoraleeae]
                 9 Leaves sessile, subsessile, or short-petiolate, the petiole < 1.5 cm long.
                     11 Stamens diadelphous; corolla purple, lavender, or cream, 5-15 mm long.
                       12 Corolla 11-15 mm long, purple; [se. and s. TX]; [tribe Diocleae]
                       12 Corolla 5-7 mm long, lavender or cream; [widespread in our area]
                          13 Flowers solitary in leaf axils; [tribe Loteae]