Mesfin Tadesse (2005) Bidens. Flora of Somalia 3: 544-547
Plants annual or perennial herbs or shrubs. Leaves opposite, petiolate; blades pinnately 3-9-lobed to pinnatisect. Inflorescences open corymbose or paniculate cymes of capitula. Capitula erect at flowering; receptacles flat to conical, with bracts between the flowers; bracts membranous, white to yellowish brown, oblong-linear, 2-9-striate; phyllaries of 2 series; outer phyllaries herbaceous, 1-3-veined; inner phyllaries membranous, grey- or orange-striate, with scarious yellow margins; ray flowers yellow or white, sterile or female, rarely with pistillodes or or staminodes; disk flowers yellow, bisexual, corollas 5-lobed; anthers brown, bases caudate or sagittate, tips with triangular-ovate appendages; style branches penicillate. Achenes flattened or tetragonal, black, striate-sulcate, variously hairy, not winged, sometimes with callose-thickened margins; pappuses usually of 2-4 stiff, backwardly barbed awns with trigonous bases, rarely pappus absent.
Bidens includes about 350 species. It is worldwide in its distribution but has centers of diversity in Africa and Mexico. There are 3 species in Somaliland, 2 of which are also known from Somalia.
