Monographs Details: Ambrosia
Authority: Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Description:Genus Description - Heads numerous, small, unisexual, rayless; staminate heads in a racemiform or spiciform, bractless infl, with subherbaceous, 5–12-lobed invol, flat receptacle with slender, filiform-setose pales, monadelphous filaments, scarcely united anthers, and undivided style; pistillate heads borne below the staminate, in the axils of lvs or bracts, with closed, nutlike or burlike invol bearing 1–several rows of tubercles or spines and containing 1(–several) pistillate fls without cor; pappus none; herbs (ours) or shrubs; lvs often lobed or dissected, in most spp. opposite at least below. 40, predominantly New World. (Franseria)