The World Flora Online

SELECTED REFERENCES

Ancibor, E. 1979. Systematic anatomy of vegetative organs of the Hydrocharitaceae. Bot. J. Linn. Soc. 78: 237--266. Catling, P. M. and W. G. Dore. 1982. Status and identification of Hydrocharis morsus-ranae and Limnobium spongia (Hydrocharitaceae) in northeastern North America. Rhodora 84: 523--545. Cook, C. D. K. 1982. Pollinating mechanisms in the Hydrocharitaceae. In: J.-J. Symoens et al., eds. 1982. Studies on Aquatic Vascular Plants. Brussels. Pp. 1--15. Godfrey, R. K. and J. W. Wooten. 1979. Aquatic and Wetland Plants of Southeastern United States:. Monocotyledons. Athens, Ga. Hartog, C. den. 1970. The Sea-grasses of the World. Amsterdam.

Herbs, annual or perennial, caulescent or without evident stem, glabrous or pubescent, entirely submersed, with both submersed and floating leaves, or with submersed stolons and emergent leaves, in fresh, brackish, or marine waters; turions rarely present. Stems rhizomatous, creeping, with abbreviated erect axis at nodes, or erect, leafy, elongate. Leaves basal, alternate, opposite, or whorled, sessile or petiolate; stipules sometimes present, forming tubular sheath around stem; blade margins entire or serrate; veins 1--many. Inflorescences axillary, terminal, or scapose, 1-flowered or cymose, subtended by spathe; spathe a 2-fid bract or pair of opposite bracts. Flowers unisexual, staminate and pistillate on same plants or on different plants, often with rudiments of opposite type, or bisexual, actinomorphic, rarely slightly zygomorphic; perianth epigynous, free, mostly 6-parted, then differentiated into sepals and petals, rarely 3-parted, then petals absent in Thalassia and Halophila; stamens (0--)2--many in 1 or more whorls (inner often staminodial), epigynous, distinct or ± connate; pollen spheric, in monads or tetrads or in slender chains; ovary 0--1, if present, inferior, 2--6[--16]-carpellate, 1-locular or falsely 6--9-locular; placentation parietal. Fruits berrylike. Seeds many, fusiform, ellipsoid, ovoid, or spheric; seed coat glabrous, papillose, or echinate.

Herbes aquatiques ou rarement terrestres, vivaces ou annuelles, des eaux douces, saumâtres ou marines, entièrement ou partiellement submergées ou parfois flottantes, à fleurs bisexuées, monoïques, dioïques, gynodioïques ou trioïques (fleurs mâles, femelles et bisexuées sur des plantes différentes) ; tiges souvent rhizomateuses ou stolonifères ou dressées, parfois cormiformes. Stipules absentes ou présentes et membraneuses. Squamules intravaginales ordinairement présentes à l’aisselle des feuilles. Feuilles en rosette basale ou insérées le long de la tige, alternes, opposées ou (sub)verticillées, pétiolées ou sessiles, à base généralement engaînante, à nervures parallèles, souvent connectées par des nervures transversales. Inflorescences en cymes ou fleurs solitaires, entourées d’une spathe formée de (1–)2 bractées opposées et libres ou soudées ; spathes souvent ailées ou côtelées. Fleurs hermaphrodites ou unisexuées, actinomorphes à légèrement zygomorphes ; hypanthium (tube périanthaire) souvent présent dans les fleurs hermaphrodites et femelles, allongé au-dessus de l’ovaire et exsert de la spathe à l’anthèse ; sépales 3, libres, souvent réfléchis, caducs ou persistants au-dessus du fruit ; pétales 3, libres ; étamines 1 à nombreuses, souvent de longueur inégale, en 1 à 5 cycles ordinairement 3-mères, souvent staminodiales, anthères à déhiscence longitudinale ; staminodes parfois présents dans les fleurs femelles ; ovaire infère, avec (2–)3 à 6(–20 ou +) carpelles, uniloculaire, à placentation pariétale ou basale, ovules 1 à plusieurs ; styles en nombre égal à celui des carpelles, les stigmates entiers ou plus souvent 2-lobés ; pistillode rudimentaire souvent présent dans les fleurs mâles. Fruits capsulaires ou bacciformes, mûrissant sous l’eau, généralement s’ouvrant de façon irrégulière, avec 1 à 200 (ou +) graines. Graines ellipsoïdales à fusiformes ou oblongues, exalbuminées ou rarement à albumen réduit ; testa lisse ou strié, côtelé, verruqueux ou tuberculé, le plus souvent densément couvert de poils unicellulaires qui se désagrègent en une masse pulpeuse enrobant la graine.

Famille comportant 18 genres et environ 130 espèces, répandues dans les régions tempérées et tropicales ; 3 genres sont marins, les autres préfèrent les eaux douces ou légèrement saumâtres. Au Gabon, il existe 2 espèces de 2 genres différentes ; un troisième genre est à rechercher.

Leaves radical or cauline, alternate to whorled Fresh-water or salt-water herbs, partly or wholly submerged; roots sometimes floating Seeds numerous, without endosperm Perianth-segments free, 1-2-seriate, 3 in each series, the outer often green, valvate, the inner petaloid Flowers hermaphrodite or unisexual, arranged in a tubular spathe or within two opposite bracts, females solitary; peduncle sometimes spirally twisted in fruit Male flowers with rudimentary ovary Stamens numerous to 2 Ovary inferior, 1-locular, with parietal placentas sometimes protruding nearly to the middle of the ovary Staminodes usually present in the female flower Fruit rupturing irregularly Ovules numerous Fresh-water or salt-water herbs, partly or wholly submerged; roots sometimes floating Seeds numerous, without endosperm Perianth-segments free, 1-2-seriate, 3 in each series, the outer often green, valvate, the inner petaloid Flowers hermaphrodite or unisexual, arranged in a tubular spathe or within two opposite bracts, females solitary; peduncle sometimes spirally twisted in fruit Male flowers with rudimentary ovary Stamens numerous to 2 Ovary inferior, 1-locular, with parietal placentas sometimes protruding nearly to the middle of the ovary Staminodes usually present in the female flower Fruit rupturing irregularly Ovules numerous

Fls regular or (Vallisneria) slightly irregular, perfect or more often unisexual; perianth of 3 distinct, green sep and 3 distinct pet, sometimes elevated on a long, slender hypanthium, or the pet or the whole perianth wanting; stamens 3–many, sometimes some of them staminodial; pistil of 3–6+ carpels weakly united to form a compound, inferior, unilocular ovary, often with ± deeply intruded partial partitions; styles as many as the carpels, often lobed or bifid, sometimes shortly connate below into a common style; placentation laminar, the ovules scattered over the surface of the partial partitions, or merely parietal (or nearly basal) when the partitions are not intruded; fr submerged, usually opening irregularly; seeds several to many, usually without endosperm; embryo straight, with an obliquely terminal cotyledon; submersed or partly emergent, rooted or free-floating aquatic herbs; infl a compact, usually few-fld cyme (especially the staminate fls) or a single fl (especially the pistillate fls), collectively subtended by (1)2 distinct or more often ± connate bracts that form a sessile to long-pedunculate spathe. 15/100.

Herbs, annual or perennial, submerged or floating, aquatic, in fresh or brackish water or marine. Stems short or elongated, sometimes stoloniferous. Leaves radical or cauline, alternate, opposite, subopposite, whorled, or pseudowhorled, sessile or petiolate, usually sheathing at base. Flowers unisexual or bisexual, actinomorphic, enclosed in a bifid spathe or within 2 opposite spathal bracts, or rarely not spatulate; spathes sessile or pedunculate. Stamens 1 to many, occasionally some staminodal; anthers 1-4-thecous. Ovary inferior, 1-loculed; carpels 2-15, fused; ovules few to many, on parietal, sometimes intruding placentae; styles 2-5; stigmas usually bifid. Fruit a fleshy and berrylike capsule dehiscent or opening by decay of pericarp, or an achene (Najas). Seeds numerous, usually small, without endosperm; embryo straight.

Monoecious, dioecious or hermaphrodite, submerged or rarely floating, freshwater or marine, annual or perennial herbs Stipules rarely present Leaves radical, or spirally arranged, or in whorls along the stem, or distichous or rarely opposite, sessile or petiolate, sometimes sheathing at the base; venation parallel or only midrib present Stems corm-like or elongate, rhizomatous, stoloniferous or erect, simple or dichotomously branched Roots mostly simple, adventitious, rarely with root hairs Perianth segments 3 or 6, the latter differentiated into sepals and petals; sepals free, usually green or whitish, often reflexed; petals free, often showy, sometimes reflexed; stamens 2–many, in 1 or more whorls; anthers 2–4-thecous, basifixed, dorsally or latrorsely, rarely introrsely or extrorsely dehiscent; filaments filiform or flattened, linear or club-shaped in outline, rarely 0; staminodes often present in ? flowers, rarely so in ? flowers, in the latter the staminodes differentiated from the inner whorl of stamens; ovary inferior, composed of 2–15 connate carpels, 1(–3)-locular; placentation parietal, rarely basal; ovules few to many, anatropus or orthotropus; styles 2–15; stigmas 2–15, entire or 2-lobed Perianth-tube (hypanthium) often present in ? and hermaphrodite flowers, exerted from or near the apex of the ovary, usually extending to carry perianth to water surface Flowers unisexual or bisexual, 1–many, mostly regular, arranged in a spathe, the spathe axillary, sessile or pedunculate and composed of 2 wholly or partly connate, rarely free, bracts Nodal scales (squamulae intravaginales) often present, situated in leaf-axils Fruit a capsule, sometimes beaked from remains of the perianth-tube, dehiscent or opening by decay of the pericarp Seeds usually minute; embryo straight with inconspicuous or conspicuous plumule; endosperm 0 Stipules rarely present Leaves radical, or spirally arranged, or in whorls along the stem, or distichous or rarely opposite, sessile or petiolate, sometimes sheathing at the base; venation parallel or only midrib present Stems corm-like or elongate, rhizomatous, stoloniferous or erect, simple or dichotomously branched Roots mostly simple, adventitious, rarely with root hairs Perianth segments 3 or 6, the latter differentiated into sepals and petals; sepals free, usually green or whitish, often reflexed; petals free, often showy, sometimes reflexed; stamens 2–many, in 1 or more whorls; anthers 2–4-thecous, basifixed, dorsally or latrorsely, rarely introrsely or extrorsely dehiscent; filaments filiform or flattened, linear or club-shaped in outline, rarely 0; staminodes often present in ? flowers, rarely so in ? flowers, in the latter the staminodes differentiated from the inner whorl of stamens; ovary inferior, composed of 2–15 connate carpels, 1(–3)-locular; placentation parietal, rarely basal; ovules few to many, anatropus or orthotropus; styles 2–15; stigmas 2–15, entire or 2-lobed Perianth-tube (hypanthium) often present in ? and hermaphrodite flowers, exerted from or near the apex of the ovary, usually extending to carry perianth to water surface Flowers unisexual or bisexual, 1–many, mostly regular, arranged in a spathe, the spathe axillary, sessile or pedunculate and composed of 2 wholly or partly connate, rarely free, bracts Nodal scales (squamulae intravaginales) often present, situated in leaf-axils Fruit a capsule, sometimes beaked from remains of the perianth-tube, dehiscent or opening by decay of the pericarp Seeds usually minute; embryo straight with inconspicuous or conspicuous plumule; endosperm 0