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DescriptionAnnual herb, glabrous with 4 rough angles. Upper cauline leaves in whorls of 5-6; margin with forwardly-directed prickles. Flowers subsessile, in small terminal heads with a basal involucre of leaf-like bracts. Calyx of 4-6 distinct teeth; these accrescent in fruit. Corolla 4-5 mm, pale lilac, the tube cylindric, as long as or longer than the lobes. Stamens 4. Style 2-fid. Fruit of 2 obovoid mericarps.