Annual to perennial, scapose, rosulate, stems mostly short, cespitose, rarely rhizomatous. Leaves equitant, distichous, sheaths open, clasping, usually broad-based, with margins entire to ciliate or fimbriate, apically either narrowing gradually or abruptly to blade or there producing a ligule or auricle, blades mostly laterally compressed and 2-margined, mostly linear, less often thickened and ventrally sulcate to terete. Scapes single or few per shoot, arising from axillary buds, sheathed at base by a single, bladeless or bladed bract, terminating in a single spike (except in no. 3); spikes cone-like, chaffy-bracted, with 1 to many flowers; bracts in spiral or decussate, the lower 2-several empty, rarely forming a "leafy" involucre, commonly grading larger into the few to many flowering bracts, all or some with thicker central zone (dorsal area) of distinctly different texture and color or lacking dorsal area entirely. Sepals 3, generally hidden by subtending bract with 2 lateral, boat-shaped, free or connate, with variously margined keel and flanking a membranaceous inner (adaxial) sepal which enfolds the corolla in bud, detaching as the flower opens; petals 3, free (rarely connate), long-clawed, only the broad blades and claw tips exserted, these mostly yellow (in Africa some are blue); staminodes 3 (rarely lacking), mostly 2-branched with branches bearded; stamens mostly with flattened filamentsand narrow, basifixed, introrse or laterally dehiscent anthers; ovary 1-or-3-locular, placentation marginal, parietal, basal, central or transitional, style tubular, slender, conduplicate, elongate, 3-branched just above petal claws, each branch terminating in a "U"-shaped stigma; stylar appendages absent. Capsules usually thinvalved; seeds (l-) few to many, mostly small and ovoid to fusiform, mostly longitudinally ribbed, opaque or translucent, embryo tiny, basal or lateral-basal.
Amazonia present, Australasia, Brazilian Planalto present, Guayana Highlands present, Guianas present, east Asia present, temperate to tropical America present, worldwide present
A genus of over 200 species worldwide, represented in east Asia and Australia and particularly in temperate to tropical America with greatest diversity and abundance in the savannas of the Guayana Highlands, in Amazonia and the Brazilian Planalto. 26 species are known from the Guianas.