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Aristolochiaceae

1. Stem creeping, rooting at the nodes, less than 10 cm long. Leaves persistent, shiny above. Flowers terminal, solitary. Stamens 12 === Asarum

1. Stem more or less erect or climbing, not rooting at the nodes, 15-90 cm or up to 20 m long. Leaves deciduous, dull above. Flowers axillary, solitary or 2-8. Stamens 6 === 2

2. Erect herbaceous perennial, stem 15-90 cm tall. Flowers solitary or in clusters of 2-8. Perianth yellowish outside, ca. 20-50 mm long. Leaves 2-7(-15) cm wide === Aristolochia

2. Woody climber, stem to 20 m long. Flowers solitary. Perianth brown-purple outside, to 80 mm long. Leaves 7-50 cm wide === Isotrema