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DescriptionAnnual or perennial herbs, erect, creeping or climbing. Stems often 4-angled, sometimes prickly. Stipules similar to the leaves. Leaves (and leaf-like stipules) in whorls of 4-10, ± sessile. Flowers in axillary or terminal cymes, bisexual, rarely unisexual, usually 4-merous, not enclosed in an involucre. Calyx reduced to a rim; teeth 0. Corolla rotate to ± campanulate, greenish, creamy-white to bright yellow. Ovary 2-locular with 1 ovule per loculus. Fruit dry, glabrous or variously hairy, consisting of two 1-seeded mericarps.