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Key to Rhynchosia

Fabaceae

Rhynchosia

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1
Leaves unifoliolate (rarely with a few upper leaves trifoliolate).
  2
Plants erect or ascending, usually with fewer than 6 leaves; stipels present
 ⇒ Rhynchosia reniformis
  2
Plant prostrate, trailing, usually with many leaves; stipels absent.
    3
Calyx 8-11 mm long, the lobes 1.5-2.0 mm wide; [s. and se. TX]
 ⇒ Rhynchosia americana
    3
Calyx 10-14 mm long, the lobes 3-4 mm wide; [FL and s. GA]
 ⇒ Rhynchosia michauxii
1
Leaves trifoliolate (rarely with a few lowermost leaves unifoliolate, these generally withering before flowering and fruiting).
  4
Plant erect; pubescence of the lower leaf surface not restricted to the veins (except in the rare upright forms of R. difformis keyed below).
    5
Terminal leaflet suborbicular, 1.0-1.3× as long as wide; plants ascending to erect (or more usually twining [keyed elsewhere])
 ⇒ Rhynchosia difformis
    5
Terminal leaflet elliptic1.6-2.5× as long as wide; plants erect.
      6
Plant lavishly branched, bushy (with something of the aspect of a Baptisia); terminal leaflets 0.5-2.0 cm long; pubescence of the lower leaf surface sparse, not velvety to the touch; flowers solitary (-3) in leaf axils
 ⇒ Rhynchosia cytisoides
      6
Plant unbranched or with few well-developed branches in its upper portion; terminal leaflets (2.0-) 2.5-5 cm long; pubescence of the lower leaf surface grayish tomentose and velvety to the touch; flowers many, in racemes.
        7
Inflorescence a single exserted terminal raceme, 5-20 cm long; stipules caducous; [plants of s. SC southward]
 ⇒ Rhynchosia mollissima
        7
Inflorescences several and axillary, each 1-3 cm long (or with a short terminal inflorescence also); stipules persistent; [plants widespread in our area]
 ⇒ Rhynchosia tomentosa
  4
Plant trailing or twining; pubescence of the lower leaf surface mostly restricted to the veins.
    8
Calyx 7-14 mm long, about as long as the corolla; [plants collectively widespread in our area].
      9
Calyx 10-14 mm long; inflorescence (including peduncle) 5-25 cm at anthesis, elongating further in fruit, with flowers scattered; [MS and w. TN westward]
 ⇒ Rhynchosia latifolia
      9
Calyx 7-10 (-12) mm long; inflorescence (including peduncle) 1-2 cm long at anthesis, elongating to 4 (-8) cm, the flowers tightly packed; [collectively widespread in our area].
        10
Terminal leaflet 1-5 cm long.
          11
Pubescence of petiole of mostly incurved hairs 0.2-0.4 mm long; terminal leaflet 1-3 (-3.5) cm long; plants generally trailing; [of ne. FL southward]
 ⇒ Rhynchosia cinerea
          11
Pubescence of petiole of mostly spreading hairs 0.5-0.6 mm long; terminal leaflet (2-) 2.5-5 cm long; plants generally twining; [widespread in our area]
 ⇒ Rhynchosia difformis
    8
Calyx 2.5-7 mm long, clearly shorter than the corolla; [plants of e. GA southward and westward].
      12
Flowers 1-3 per inflorescence; leaflets 2.2-5× as long as wide; [se. TX and s. TX southwards and westwards]
 ⇒ Rhynchosia texana
      12
Flowers 2-15 per inflorescence; leaflets 0.8-2.5× as long as wide; [e. GA southwards and westwards, including se. and s. TX].
        13
Calyx 2.5-3 (-4) mm long; raceme 4-12 cm long, clearly exceeding the subtending leaves; leaflets 0.8-1.2× as long as wide; [e. GA southwards and westwards]
 ⇒ Rhynchosia minima
        13
Calyx 3.5-7 mm long; raceme 1-4 (-5) cm long, barely if at all exceeding the subtending leaves; leaflets 1.2-2.5× as long as wide; [plants of s. peninsular FL].
          14
Lower surface of leaflet cinereous-villosulous, the hairs largely obscuring the glands; seeds brown
 ⇒ Rhynchosia parvifolia

© Scott Ward
          14
Lower surface of leaflet inconspicuously puberulent, the yellow glands evident; seeds red or red-and-black.
             15
Leaflets (4-) 6-8 cm long; seeds red and black; legume 9-12 mm wide
 ⇒ Rhynchosia precatoria
             15
Leaflets 2-4 (-6) cm long; seeds red; legume 5-8 mm wide
 ⇒ Rhynchosia swartzii