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.
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.
Seeds numerous, without endosperm
Leaves radical or cauline, alternate to whorled
Fresh-water or salt-water herbs, partly or wholly submerged; roots sometimes floating
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
Ovary inferior, 1-locular, with parietal placentas sometimes protruding nearly to the middle of the ovary
Staminodes usually present in the female flower
Fruit a capsule, sometimes beaked from remains of the perianth-tube, dehiscent or opening by decay of the pericarp
Monoecious, dioecious or hermaphrodite, submerged or rarely floating, freshwater or marine, annual or perennial herbs
Seeds usually minute; embryo straight with inconspicuous or conspicuous plumule; endosperm 0
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
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.
|Tape-grass or Frog-bit Family|