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Published In: Genera Plantarum 67. 1789. (4 Aug 1789) (Gen. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 7/22/2009)


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Plants herbaceous perennials, monoecious, dioecious, or less commonly with perfect flowers, sometimes with stolons. Stems short and erect or elongate and branched. Leaves opposite, whorled, or essentially basal, simple. Inflorescences short- to long-pedunculate, 1- to few-flowered cymes enclosed by a spathe of 2 bracts, these sometimes more or less fused together. Flowers actinomorphic or less commonly slightly zygomorphic. Sepals 3, distinct. Petals 3, distinct. Stamens 3 to many, some of them sometimes modified into staminodes. Pistils 1 per flower, of 3–6 or more carpels united to form a compound, inferior, 1-locular ovary. Styles 3–6 or more, sometimes fused at the base, sometimes 2-branched or 2-lobed above, each branch with 1 stigma. Fruits berrylike, with numerous small seeds. Fifteen genera, about 100 species, worldwide.

The Hydrocharitaceae are mostly submerged aquatics, although plants of some genera are sometimes floating-leaved, whereas others often grow emergent on mud. The flowers have a variety of unusual pollination mechanisms. The berrylike fruits usually are submerged at maturity. Most of the species are important wildlife food plants.


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1 Leaves basal, ribbonlike, elongate, 60–200 cm long 4 Vallisneria
+ Leaves basal or cauline, cordate to narrowly oblong, or if linear then 0.6–4.0 cm long (2)
2 (1) Leaves cordate to broadly spathulate, petioled, the undersurface usually with a spongelike mass of enlarged cells near the base 3 Limnobium
+ Leaves linear to narrowly oblong, less commonly narrowly ovate near the base of the plant, without a spongelike mass of enlarged cells on the undersurface (3)
3 (2) Main leaves in whorls of 4–6; petals showy, longer than the sepals 1 Egeria
+ Main leaves in whorls of 3 or opposite; petals not showy, shorter than to about as long as the sepals 2 Elodea
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