5474.000 Ammannia L.

Annual, glabrous herbs. Stems erect or decumbent, 4-gonous or 4-winged, simple or ± branched. Leaves decussate, sessile, entire, 1-nerved; bracteoles small, membranous, whitish. Flowers 4 (5–8)-merous, never heterostylous. Calyx campanulate or urn-shaped, 8-ribbed; appendages absent or very short. Petals 4–8, very caducous or absent, small, obovate, spathulate or rounded. Stamens as many as or twice the number of calyx-lobes, rarely fewer, with the filaments inserted at 1/4–1/2 of the calyx-tube length; anthers didymous. Ovary incompletely 2–4(5)-locular, sometimes unilocular; stigma capitate; ovules numerous, axile or on the septa. Fruit capsule globose or ellipsoid, included in the calyx or ± exserted, thinly membranous, dehiscing transversally and irregularly; seeds numerous, very small, angular.

Worldwide: Species 20, cosmopolitan.

Zimbabwe: 5 taxa.