The World Flora Online

SELECTED REFERENCES

Hagström, J. O. 1916. Critical researches on the potamogetons. Kungl. Svenska Vetenskapsakad. Handl., n. s. 55(5): 1--281. Haynes, R. R. 1978. The Potamogetonaceae in the southeastern United States. J. Arnold Arbor. 59: 170--191. Les, D. H. 1983. Taxonomic implications of aneuploidy and polyploidy in Potamogeton (Potamogetonaceae). Rhodora 85: 301--323. Mason, H. L. 1957. A Flora of the Marshes of California. Berkeley. Reveal, J. L. 1977b. Potamogetonaceae. In: A. Cronquist et al. 1972+. Intermountain Flora. Vascular Plants of the Intermountain West, U.S.A. 5+ vols. New York and London. Vol. 6, pp. 24--42. Thorne, R. F. 1993b. Potamogetonaceae. In: J. C. Hickman, ed. 1993. The Jepson Manual. Higher Plants of California. Berkeley, Los Angeles, and London. Pp. 1304--1308.

Herbs, perennial or rarely annual, rhizomatous or not rhizomatous, caulescent; turions absent or present. Leaves alternate or nearly opposite, submersed or both submersed and floating, sessile or petiolate; sheath not persisting longer than blade, not leaving circular scar when shed, ligulate, not auriculate, or rarely auriculate; intravaginal squamules scales, more than 2. Inflorescences terminal or axillary, spikes, capitate spikes, or panicles of spikes, not subtended by spathe, pedunculate; peduncle not elongating, not spiraling following fertilization. Flowers bisexual; subtending bracts absent; tepals 4 in 1 series; stamens [2 or] 4, epitepalous, in 1 series; anthers distinct, dehiscing vertically; pollen spheric; pistils 1 or 4, mostly not stipitate, rarely short-stipitate; ovules marginal, orthotropous. Fruits drupaceous. Seeds 1; embryo curved.

Herbes aquatiques, annuelles ou pérennes, des eaux douces ou saumâtres, stagnantes ou vives, s’enracinant au substrat, glabres ; rhizomes souvent présents ; tiges souvent branchues, parfois flottantes, les parties flottantes parfois à feuilles d’une forme différente de celles des feuilles submergées. Stipules généralement présentes, libres ou réunies en une gaine tubulaire, parfois fusionnées avec la base de la feuille. Feuilles alternes ou subopposées, rarement ternées (Groenlandia et Zannichellia), simples, sessiles ou pétiolées ; limbe à marge entière, denticulée ou serrée. Inflorescences axillaires ou terminales, souvent en épis pédonculés, épis parfois interrompus ou capités, ou parfois inflorescence sessile avec 1 à 3 fleurs axillaires. Fleurs actinomorphes, bisexuées ou unisexuées et espèces monoïques ou rarement dioïques ; tépales 3 ou 4, libres, valvaires, onguiculés, ou réunis en un tube ou une soucoupe ; étamines 1, 2 ou 4, anthère généralement sessile ; gynécée supère, composé de 1 à 8 carpelles libres ou courtement unis à la base, à 1 ovules par loge ; style court, à 1 stigmate. Fruits apocarpiques, s’ouvrant avec un couvercle ou indéhiscents. Graines à embryon courbé.

Les Potamogetonaceae comprennent cinq genres (Althenia, Groenlandia, Potamogeton, Stuckenia et Zannichellia), dont les trois derniers présents en Afrique tropicale, qui englobent environ 85 espèces. Au Gabon, seulement un genre avec une espèce a été signalé.

Plantes herbacées, vivaces, rarement annuelles, aquatiques ou rampant occasionnellement sur la vase.'Feuilles'alternes ou opposées, rarement ternées, sessiles ou pétiolées, parfois embrassantes à la base, souvent hétéromorphes; stipules libres ou soudées entre elles en une ligule dégagée ou adnée à la base du limbe, manquant parfois aux feuilles caulinaires, accompagnées de petites squamules axillaires; limbe le plus souvent entier, parfois denticulé, terminé par un pore aquifère. Inflorescences axillaires, pédonculées, simples, en épis ovoïdes ou cylindriques, émergeant ordinairement à la floraison.'Fleurs'actinomorphes, bisexuées; périgone à 4 tépales libres, petits; étamines 4, opposititépales; anthères sessiles, à 2 thèques bisporangiées, extrorses, à déhiscence longitudinale; carpelles (1-)4, alternant avec les étamines, supères, libres ou partiellement adnés; ovules solitaires, insérés dans l'angle adaxial du carpelle, pendants, subatropes, bitégumentés; style court.'Fruits': drupes ou akènes.'Graines exalbuminées; embryon courbe, à hypocotyle épais.\n\t\t\tFamille cosmopolite comprenant 2 genres et environ 100 espèces. Pour la Flore : 1 genre et 5 espèces.

Carpels 4, free, 1-locular; stigmas sessile or on short styles; ovule solitary, on the adaxial angle Seeds without endosperm Stamens 4, inserted in the claws of the segments; anthers extrorse, 2-locular, sessile Fruits free, 1-seeded, indehiscent Flowers hermaphrodite, small, arranged in pedunculate axillary spikes; peduncle surrounded by a sheath at the base; bracts absent Perianth of 4 free rounded shortly clawed valvate segments Aquatic herbs of fresh, water Leaves alternate or opposite, those immersed thin, those above water often leathery, sheathing at the base, sheath free or partially adnate to the petiole Seeds without endosperm Stamens 4, inserted in the claws of the segments; anthers extrorse, 2-locular, sessile Fruits free, 1-seeded, indehiscent Flowers hermaphrodite, small, arranged in pedunculate axillary spikes; peduncle surrounded by a sheath at the base; bracts absent Perianth of 4 free rounded shortly clawed valvate segments Aquatic herbs of fresh, water Leaves alternate or opposite, those immersed thin, those above water often leathery, sheathing at the base, sheath free or partially adnate to the petiole

Fls small, perfect, regular, tetramerous throughout, anemophilous or less often hydrophilous, borne in axillary or terminal, bractless, often somewhat fleshy spikes that in most spp. are elevated a little above the water; perianth a single whorl of 4 distinct, fleshy-firm, valvate, shortly clawed tep; stamens 4, opposite the tep and basally adnate to the claw; anthers virtually sessile, extrorse; pollen inaperturate; ovaries (1–)4, distinct, alternating with the stamens, each with a short terminal style or a sessile stigma; ovule solitary, marginal or basal-marginal; fr of distinct achenes or drupelets, generally buoyant in the water, the pericarp aerenchymatous; endosperm wanting; embryo with a large hypocotyl and an obliquely terminal cotyledon that encloses the plumule; glabrous perennial herbs of fresh (seldom brackish) water, rooted in the substrate, most spp. with creeping sympodial rhizomes; lvs alternate or sometimes (especially the uppermost) subopposite, all submersed or some floating, parallel-veined (or with a single midvein), with a well developed basal open or closed sheath, the blade or petiole sometimes attached near the top of the sheath, which projects beyond as a ligule, more often attached farther down the sheath or directly to the node, so that the sheath appears to form an intrapetiolar stipule. A single genus.

Herbs, perennial or annual, in fresh to brackish water, totally submerged or with floating leaves. Rhizomes present or absent. Stems elongated or shortened, terete to compressed, rarely strongly compressed. Leaves alternate or basal, occasionally opposite or subopposite; stipules free from leaves or adnate to leaf base and sheathing stems. Inflorescence a capitate spike, terminal or axillary. Plants monoecious; flowers small, bisexual. Perianth bractlike, free, present or absent. Stamens (1-)4; anthers sessile, (1 or)2-celled, extrorse, longitudinally dehiscent. Carpels (1-)4, free; ovule solitary. Fruit drupaceous. Embryo curved; endosperm absent.

Leaves alternate or subopposite, rarely ternate, sessile or petiolate, simple, served by 3 traces, parallel-veined or with a single midvein; stipules present throughout or only on young shoots ( Groenlandia ), often forming a tubular sheath around the stem and young inflorescence, either free or adnate to the base of the blade; intravaginal scales 2– several, situated in leaf axils, mostly linear to subulate, rarely ovate, entire and acute; bladeentire, denticulate or serrate Vegetative shoot system comprising horizontal shoots, mostly stoloniferous, non chlorophyllous (here called rhizomes) and vertical shoots, erect or sometimes ± floating, often densely branched, chlorophyllous (here called stems); tubers or turions sometimes present on the horizontal and/or the erect shoots Flowers& #2695; (hermaphrodite), small, regular, hypogynous, tetramerous Inflorescences pedunculate, with 2 opposite flowers ( >i>Groenlandia ) or more than 2 flowers in a dense or interrupted spike ( >i>Potamogeton ); peduncle rigid and mostly slightly elevated above the water level, but sometimes flexuous, the flowers resting then on the water surface, rarely submerged, but often withdrawing the fruits below the surface; bracts abortive or absent Stamens 4, opposite the tepals and basally adnate to the claw; anthers sessile, bilocular, extrorse, opening by longitudinal slits Perianth: a singlewhorl of 4 valvate shortly clawed tepals Aquatic herbs, perennial or rarely annual, glabrous, rooted in the substrate Gynoecium superior, of (1– 3) 4 (5– 8) carpels, sessile, free or shortly connate at the base, alternating with the stamens; styles usually short; stigma unicellular-papillate and strongly secretory or smooth and dry or weakly secretory; ovule solitary in the carpel and attached to its ventral margin, orthotropous at first, but becoming campylotropous at maturity, pendant and filling the locule, bitegmic, crassinucellate Seed without endosperm; embryo unciform or spiral (i.e. coiled more than 1 complete turn), with a large hypocotyl and a single obliquely terminal cotyledon that encloses the plumule Fruit apocarpous consisting of distinct sessile fruitlets, ± drupaceous, but opening with a dorsal lid, with a rather fleshy parenchymatous mesocarp and a sclerified endocarp, the latter multi-layered ( >i>Potamogeton )or 1-layered ( >i>Groenlandia ) Vegetative shoot system comprising horizontal shoots, mostly stoloniferous, non chlorophyllous (here called rhizomes) and vertical shoots, erect or sometimes ± floating, often densely branched, chlorophyllous (here called stems); tubers or turions sometimes present on the horizontal and/or the erect shoots Flowers& #2695; (hermaphrodite), small, regular, hypogynous, tetramerous Inflorescences pedunculate, with 2 opposite flowers ( >i>Groenlandia ) or more than 2 flowers in a dense or interrupted spike ( >i>Potamogeton ); peduncle rigid and mostly slightly elevated above the water level, but sometimes flexuous, the flowers resting then on the water surface, rarely submerged, but often withdrawing the fruits below the surface; bracts abortive or absent Stamens 4, opposite the tepals and basally adnate to the claw; anthers sessile, bilocular, extrorse, opening by longitudinal slits Perianth: a singlewhorl of 4 valvate shortly clawed tepals Aquatic herbs, perennial or rarely annual, glabrous, rooted in the substrate Gynoecium superior, of (1– 3) 4 (5– 8) carpels, sessile, free or shortly connate at the base, alternating with the stamens; styles usually short; stigma unicellular-papillate and strongly secretory or smooth and dry or weakly secretory; ovule solitary in the carpel and attached to its ventral margin, orthotropous at first, but becoming campylotropous at maturity, pendant and filling the locule, bitegmic, crassinucellate Seed without endosperm; embryo unciform or spiral (i.e. coiled more than 1 complete turn), with a large hypocotyl and a single obliquely terminal cotyledon that encloses the plumule Fruit apocarpous consisting of distinct sessile fruitlets, ± drupaceous, but opening with a dorsal lid, with a rather fleshy parenchymatous mesocarp and a sclerified endocarp, the latter multi-layered ( >i>Potamogeton )or 1-layered ( >i>Groenlandia )