Habit and leaf form. Aquatic herbs. Plants more or less succulent (the branches and petioles spongy and aerenchymatous). Annual, or perennial. Leaves basal, or basal and cauline (several at base and 1 on the flowering stem). Plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves; rhizomatous (very reduced). Hydrophytic; free floating, or rooted (sometimes). Leaves submerged, or emergent, or floating; alternate (clustered); spiral, or distichous; petiolate (petiole of basal leaf swollen and spongy); sheathing. Leaf sheaths tubular. Leaves simple. Leaf blades entire; oblong (transverse), or linear (or broader), or orbicular (almost), or rhombic; parallel-veined (numerous, or finely curvinerved); without cross-venules; cordate, or attenuate at the base. Leaves ligulate, or eligulate; without stipules. Leaf blade margins entire (or often undulate). Leaf anatomy. Hairs absent (more or less). Extra-floral nectaries absent. Stem anatomy. Secondary thickening absent.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Plants homostylous, or heterostylous. Floral nectaries present. Nectar secretion from the gynoecium (via septal nectaries). Entomophilous.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in spikes, or in panicles (rarely). The terminal inflorescence unit cymose, or racemose. Inflorescences terminal; flowering stem erect; inflorescence arising from sheath-like bract above the cauline leaf; spike of few to many flowers; spatheate, or espatheate. Flowers bracteate (bract blade present or usually absent); ebracteolate; small to medium-sized; very irregular; zygomorphic. The floral asymmetry involving the perianth, or involving the perianth and involving the androecium. Flowers 3 merous; pentacyclic. Perigone tube present. Free hypanthium filaments adnate to the perianth tube. Perianth of ‘tepals’; 6 (in 2 whorls); 2 -whorled; isomerous; free, or joined; petaloid; without spots, or spotted; similar in the two whorls; blue. Androecial members definite in number. Androecium 6. Androecial members free of the perianth; markedly unequal (3 longer); free of one another; 2 -whorled (3+3). Androecium exclusively of fertile stamens. Stamens 6; all more or less similar in shape; diplostemonous; in 2 whorls at base of the perianth; alterniperianthial. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse. Gynoecium 3 carpelled. The pistil 3 celled. Carpels isomerous with the perianth. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary plurilocular; 3 locular; sessile. Gynoecium stylate. Styles 1; attenuate from the ovary; apical. Stigmas 1; 3 - lobed. Placentation axile. Ovules 20–50 per locule (many); pendulous; non-arillate; anatropous.
Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Fruit 3 celled; 20–100 seeded (many). Seeds endospermic. Endosperm not oily. Embryo well differentiated. Cotyledons 1. Embryo straight.
Economic uses, etc. Eichhornia (water hyacinth) is a watergarden ornamental and a devastating weed of waterways.
Etymology. After Johann Albrecht Friedrich Eichorn (1779–1856) of Berlin, a Prussian court adviser and politician.