Pontederiaceae

Abstract

Pontederiaceae, in the order Commelinales according to the APG II system, is a family of monocotyledonous flowering plants. It is a small family of heterostylous aquatic plant, occurring in tropical and subtropical regions, although not all of the species are heterostylous. The family contains 34 known species, belonging to six genera, including one best-known species, the water hyacinth (Eichhornia crassipes), an invasive species worldwide. The plants in the family are usually aquatic, annual or perennial herbaceous, with numerous fibrous roots, and occasionally endowing with procumbent stolons. Leaves are usually ovate to linear and petioles sheathed. Flowers are bisexual, solitary or arranged to racemose, spicate or paniculate, and often subtended with sheathes. Perianth segments are 6, 2-whorled, and petal-like. Stamens are usually six. Filaments are free. Anthers are 2-loculed. Ovary is superior and placentation axile or parietal. Ovules are often anatropous. Styles are one. Stigmas are capitate or 3-fid. Fruit is usually a capsule, 3-valved. Seeds are ribbed longitudinally, with embryo straight. Three species, belonging three different genera, are illustrated in this chapter.