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DescriptionAnnual herbs. Leaves opposite, simple, strongly 3-nerved from the base; bases sometimes connate. Capitula numerous, sessile, aggregated in dense sessile glomerules or cymes, heterogamous; ray florets 1 to few, with inconspicuous, yellow ligule. Phyllaries 2-3-seriate, usually with smaller outer bracts. Achenes narrowly obovoid, somewhat flattened, black, 8-10-ribbed. Pappus 0.