Herbs, annual or perennial, aquatic, rooted in mud or free-floating. Stems of 2 types, vegetative and flowering; vegetative stems indeterminate, bearing many leaves, glabrous; flowering stems determinate, usually emersed, bearing single leaf, spathe, and terminal inflorescence. Leaves of 2 types, sessile and petiolate; stipule marcescent, apex truncate, associated with petiolate leaves only; sessile leaves submersed or rarely emersed, forming basal rosette or alternate on elongate stem, blade linear to occasionally oblanceolate, base sheathing, margins entire; petiolate leaves floating or emersed, blade cordate, reniform, or ovate. Inflorescences paniculate, spicate, umbellate, or 1-flowered; spathes bractlike, folded or clasping, commonly with acute to caudate extension. Flowers sessile, 3-merous; perianth with tepals connate proximally, yellow, blue, mauve, or white, tube tubular or funnelform, limb 6-lobed; stamens 3 or 6, adnate to perianth; pistils 3-locular, 1 or 3 developing to maturity; placentation parietal or basal; ovules 1–many. Fruits capsular or utriculate. Seeds smooth or with longitudinal wings.

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• 3
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Herbs annual or perennial, aquatic, floating or rooting in substrate. Roots fibrous. Vegetative stems short or creeping, thick. Leaves rosulate or distributed along stem, distichous; petiole mostly distinct, sometimes inflated; leaf sheath usually present; leaf blade emersed or submersed, broadly ovate, lanceolate, or broadly linear, sometimes completely reduced, stomata paracytic. Flowering stems erect, solid, terminating in a leaf, spathe, and inflorescence. Inflorescences paniculate, racemose, spicate, umbellate, or 1-flowered, subtended by a spathelike or tubular leaf sheath; bracts minute or absent. Flowers bisexual, mostly actinomorphic, sometimes zygomorphic. Perianth segments 6, in 2 whorls, petaloid, free or basally connate into a tube. Stamens usually 6 in 2 whorls, rarely 3 or 1, inserted on perianth, often unequal or dissimilar; filaments slender, free; anthers 2-loculed, introrse, dehiscing by longitudinal slits or rarely by pores; pollen grains 2- or 3-nucleate, colpi 1 or 2(or 3), distal or subequatorial. Ovary superior, 3-loculed and placentation axile or 1-loculed and placentation parietal; ovules numerous per locule or 1 and pendulous, anatropous. Style 1; stigma capitate or minutely 3-lobed. Fruit a 3-valved capsule or indehiscent. Seeds small, longitudinally ribbed or smooth; endosperm copious, mealy; embryo central in seed, straight, terete.

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• 4
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Ovary superior, 3-locular, with axile placentas or 1-locular with 3 parietal placentas; style entire or shortly lobed

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• 1
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Stamens 6 or 3, rarely 1, inserted on the perianth, sometimes somewhat unequal in length or 1 the longest of all; filaments free; anthers 2-locular, opening lengthwise by slits or rarely by pores

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• 1
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Fruit a capsule opening by 3 valves, or indehiscent

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• 1
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Ovules numerous to solitary and then pendulous

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• 1
]. 

Aquatic erect or floating herbs

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• 1
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Leaves with floating or immersed blades sheathing at the base

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• 1
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Flowers bisexual, actinomorphic, arranged in racemes or panicles subtended by a spathe-like leaf-sheath; bracts minute or absent

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• 1
]. 

Perianth hypogynous, corolline; lobes 6 or 4, sub-biseriate

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• 1
]. 

Seeds ribbed, with copious endosperm

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• 1
]. 

Seeds longitudinally ribbed, with copious endosperm

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• 2
]. 

Leaves with floating and/or emersed blades, sheathing at the base

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• 2
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Flowers hermaphrodite, regular or slightly irregularly two-lipped, arranged in racemes, spikes, panicles or sub-umbellate inflorescences subtended by a spathe-like leaf-sheath or solitary (Eichhornia)

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• 2
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Erect or floating aquatic herbs

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• 2
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Ovary superior, 3-locular with axile placentas or unilocular with 3 parietal placentas; style entire or lobed; ovules anatropous, numerous to solitary

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• 2
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Fruit a capsule opening by 3 valves, or an indehiscent achene

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• 2
]. 

Perianth hypogynous, petaloid, divided into 6 lobes more or less arranged in two series, united at the base or free

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• 2
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Stamens 1, 3, or 6, equal or unequal, inserted on the perianth; filaments free; anthers dithecous, opening by longitudinal slits or rarely by terminal pores

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• 2
]. 

Herbes'vivaces et rhizomateuses, ou rarement annuelles, palustres ou aquatiques, enracinées au fond de l'eau ou flottant librement.'Feuilles'opposées, verticillées par 3-4, ou alternes, souvent toutes en rosette basilaire, munies à leur base d'une gaine entourant la tige, souvent pétiolées; limbe nageant, flottant ou aérien. Epis, racèmes ou panicules, rarement fleurs solitaires; bractées sous-tendantes petites ou absentes.'Fleurs'aériennes et entomogames, parfois submergées et cléiostogames, généralement 3-mères, bisexuées, à symétrie presque rayonnante ou bilatérale médiane, souvent un peu bilabiées; tépales en 2 verticilles ± distincts, pétaloïdes, unis à leur base en un tube ± long ou libres; étamines égales ou inégales, insérées sur les tépales, soit 6 en 2 verticilles, soit 3 fertiles en un verticille, soit 2 fertiles accompagnées d'un staminode, soit une fertile accompagnée de 2 staminodes; filets libres entre eux; anthères dithèques, déhiscentes par fentes longitudinales ou rarement par pores apicaux; ovaire supère, syncarpe, 3-loculaire à placentation axile ou 1-loculaire à 3 placentas pariétaux, surmonté d'un style filiforme entier ou courtement 3- ou 6-lobé; présence de glandes septales; ovules anatropes, pendants, nombreux à solitaires.'Capsules'loculicides, déhiscentes en 3 valves, à graines nombreuses, ou fruits indéhiscents, monospermes, entourés du périgone devenu charnu (anthocarpes).'Graines ornées de lignes longitudinales; embryon droit, cylindrique; albumen abondant, amylacé.\n\t\t\tFamille comprenant 7-8 genres et environ 30 espèces, de plantes palustres ou aquatiques d'eau douce en zone intertropicale, avec irradiations jusque dans les zones tempérées nord et sud. Pour la Flore : 3 genres et 4 espèces, dont une introduite.

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• 5
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SELECTED REFERENCES

Alexander, E. J. 1937. Pontederiaceae. In: N. L. Britton et al., eds. 1905+. North American Flora…. 47+ vols. New York. Vol. 19, pp. 51–60. Barrett, S. C. H. and D. E. Seaman. 1980. The weed flora of California rice fields. Aquatic Bot. 9: 351–376. Eckenwalder, J. E. and S. C. H. Barrett. 1986. Phylogenetic systematics of Pontederiaceae. Syst. Bot. 11: 373–391. Kaul, R. B. and C. N. Horn. 1986. Pontederiaceae. In: Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, Kans. Pp. 1239–1241. Rosatti, T. J. 1987. The genera of Pontederiaceae in the southeastern United States. J. Arnold Arbor. 68: 35–71. Solms-Laubach, H. 1883. Pontederiaceae. In: A. L. P. P. de Candolle and C. de Candolle, eds. 1878–1896. Monographiae Phanerogamarum.... 9 vols. Paris. Vol. 4, pp. 501–535.

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• 3
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