Centaurium Hill

Herbs, annual, biennial, or perennial, often with a basal rosette of leaves; stems erect to procumbent at the base, terete to angulate, often branched. Leaves sessile to subsessile, occasionally amplexicaul. Inflorescences of loose cymes, corymbiform or capituliform with a usually sessile central flower, or the cymes unpaired and spicate, or in reduced dichasia, or the flowers solitary. Flowers with 2 opposite bracts, 4-to 6-merous; calyx tubular at the base, the lobes cari-nate; corolla contorted, dextrorse, usually pink, sometimes yellow or white, the tube cylindrical, shorter to longer than the lobes, the lobes spreading to ascend-ing at anthesis; stamens with the filaments filiform, inserted on the corolla tube, the anthers introrse, subbasifixed and spirally twisting at maturity; ovary sessile, elongate, 1-celled, the placentae often intruded, the style filiform, exserted, the stigmas bilamellate. Capsules elongate, surrounded by the marcescent calyx and corolla, septicidally 2-valvate; seeds minute, variously shaped, the testa finely reticulate. Pollen grains in monads, radially symmetrical, isopolar, subprolate to prolate, the amb rounded-triangular, 24-29 x 18-23 ,u, 3-colporate, the colpi relatively long with tapering, ? acute ends, the colpus membrane smooth or finely granular, the ora usually lolongate with lateral extensions, the diameter of apocolpia 6-7 ,u; exine 3 ,u thick; sexine thicker than nexine, striate, striate-reticulate, rarely reticulate, the lirae (muri) 0.6-0.8 microns wide, parallel or not, crisscrossed (C. quitense, C. strictum).