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Herbs, usually biennial or perennial, sometimes annual, sometimes subshrubs or small shrubs. Lvs usually opposite and decussate, free or connate at base, simple, entire, toothed or rarely pinnatifid, not crowded in terminal rosettes. Infl. a corymbose, paniculate or thyrsoid cyme, usually terminal with many fls. Fls 4-merous, ± erect. Calyx divided from c. 1/2 way to almost the base; lobes equal. Petals somewhat fleshy, forming a tube > lobes; lobes free, erect to reflexed, white, yellow to deep red, or sometimes purplish; tube rather narrowly cylindric, 4-angled. Stamens 8, in 2 unequal whorls, epipetalous, usually included. Scales free, very variable in shape. Carpels 4, slightly connate at base. Seeds numerous.