Heads radiate or disciform; invol a single series of green bracts; outer fls pistillate and fertile, the cor with or without an expanded, yellow to white ray; receptacle flat or nearly so, chaffy throughout, the bracts subtending the pistillate fls larger and more herbaceous than those of the disk; disk-fls sterile, with undivided style; ray-achenes thick, not much compressed, glabrous or shortly hairy distally; pappus none; perennial herbs (ours) or shrubs with large, opposite (or the upper alternate) lvs and several to many medium-sized subhemispheric heads. 20, New World.
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