Ludwigia

Genus Ludwigia L. Description

Herbs erect or prostrate, subshrubs to trees, terrestrial or aquatic plants; branches pubescent to glabrescent. Leaves alternate, generally sessile to subsessile; stipules generally lacking or reduced. Flowers solitary, axillary, pedicellate or sessile; bracteoles absent or conspicuous, normally 2, near the base of hypanthium; calyx 4–5-merous, dialysepalous, green or reddish, persistent; corolla 4–5–(6)-merous, dialypetalous, yellow or white, deciduous; androecium isostemonous or diplostemonous, disposed in two series, epipetalous shorter than the episepalous, stamens inserted at the base of the epigynous disk together with the petals; hypanthium not extended above the ovary, cylindrical or angular, 4–5-carpellar, 4–5-locular, ovaries numerous, placentation axial, stigma capitate, globose, slightly lobular, the number of lobules corresponds to the number of locules; nectariferous disk generally plain or convex, on the ovary, nectary depressed, covered with indumentum of white trichomes. Fruit a capsule. Seeds small, numerous, uni- or pluriseriate in each locule, free or embedded in endocarp, generally with inconspicuous raphe, in some sections it may be expanded and equal in size to the body of the seed, or rarely expanded and wing-shaped (Ludwigia sect. Arborescentes Zardini & P.H.Raven).

The genus Ludwigia is pantropical. It is the only genus of the subfamily Ludwigioideae, composed of 83 species grouped in 23 sections, considered the most distinct genus of Onagraceae. Ten sections are distributed in South America, five in Africa, three in North America, three in Asia and two are not restricted to any continent. Main diversity centers are South America and North America (Wagner et al. 2007; Pesamosca & Boldrini 2015).

Specimens of Ludwigia were mainly collected from humid, flooded and aquatic environments (Fig. 2).

In Brazil, species vernacular names are ‘cruz-de-malta’ or ‘pimenta-d’água’.