Onagraceae

Annual or perennial herbs (in Mal.), occasionally somewhat woody near the base, sometimes aquatic. Leaves spiral or opposite. Stipules absent or reduced, deltoid. Flowers mostly 4-merous, rarely 5-merous (in Mal.), solitary or arranged in a terminal racemose inflorescence, subtended by (often reduced) leaves or bracts. Bracteoles absent or 2 at the base of the ovary. Floral tube short or absent. Sepals erect, persistent. Petals caducous, contorted in aestivation, white, pink or yellow, sometimes emarginate. Stamens 4, 5, 8, or 10, in 2 whorls, rarely with an intermediate number, epipetalous ones sometimes shorter. Anthers usually versatile, sometimes seemingly basifixed by reduction: pollen single or in tetrads. Ovary inferior, (in Mal.) 4- or 5-celled and with ~ ovules; summit of the ovary (disk) flat to conical (in Mal.), sometimes with depressed nectaries surrounding the bases of the epipetalous stamens. Style simple; stigma capitate, clavate or globose, often 4-lobed. Ovules with axial placentation, 1-pluriseriate. Fruit (in Mal.) a mostly long and slender loculicidal or irregularly rupturing capsule. Seeds rounded or elongate, in Ludwigia sometimes embedded in powdery or surrounded by cork-like endocarp tissue, in Epilobium with a chalazal plume of trichomes (coma); endosperm absent; embryo straight. Distribution. About 17 genera and more than 600 spp. in tropical and temperate regions, with a distinct centre of diversity on the northern hemisphere in the New World, in Malesia two native genera which are both almost ubiquist.