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Key to Aristolochia

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1 Low, erect or ascending herb or (Aristolochia pentandra) a twining herbaceous vine; leaves 0.5-6.5 cm wide.

2 Leaf bases cuneate; gynoecium and androecium 5-merous  Aristolochia erecta

2 Leaf bases cordate; gynoecium and androecium 3-, 5-, or 6-merous.

Show caption*© Roger L. Hammer     3 Twining herbaceous vine; gynoecium and androecium 5-merous  Aristolochia pentandra

3 Erect or ascending herb; gynoecium and androecium 3- or 6-merous.

4 Leaf blade as wide as long, or wider than long; leaf venation palmate  Aristolochia clematitis

4 Leaf blade narrower than long; leaf venation pinnate (3-veined from the base, pinnate above)  Endodeca

1 Woody, twining vine; leaves 3-35 cm wide

5 Gynostemium lobes 3; calyx limb 3-lobed, the lobes similar in size and shape and arranged radially around the tube orifice at 120 degree angles  Isotrema

5 Gynostemium lobes 6; calyx limb 1- or 2-lobed (if 2-lobed, the lobes dissimilar in shape)

6 Leaf base rounded to truncate; leaf venation pinnate  Aristolochia maxima

6 Leaf base cordate; leaf venation palmate.

7 Calyx limb 1-lobed, orbicular, 10-50 cm in diameter

8 Calyx limb about 10 cm in diameter, notched at the bottom  Aristolochia elegans

8 Calyx limb 20-50 cm in diameter, attenuate at the bottom into an elongate dangling appendage  Aristolochia grandiflora

7 Calyx limb 2-lobed, the lower lanceolate, acuminate, folded longitudinally and bird-beak-like, 10-20 cm long, the upper with a parallel-sided claw and orbicular tip.

9 Upper lobe of calyx limb 14-18 cm wide, with ruffled margin, pendent below the lower lip  Aristolochia labiata

9 Upper lobe of calyx limb 4-5 cm wide, not ruffled, erect over the lower lip  Aristolochia ringens