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DescriptionErect, perennial herb with tuberous roots. Leaves opposite. Inflorescence cymose. Involucre of connate bracts calyx-like, 5-lobed. Flowers conspicuous, bisexual, ephemeral. Perianth tubular, with expanded 5-lobed limb; lower part persistent in fruit, upper part coloured. Stamens 5-6 (in ours), unequal. Fruit enclosed in a hardened perianth base.