''Zannichellia'' (common name horned pondweed) is a genus of submerged aquatic

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

, with threadlike

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

and tiny

flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...

s. It is fully adapted to an aquatic life cycle, including underwater

pollination Pollination is the transfer of pollen from an anther of a plant to the stigma (botany), stigma of a plant, later enabling fertilisation and the production of seeds. Pollinating agents can be animals such as insects, for example bees, beetles or bu ...

. There are perhaps five species, including '' Zannichellia palustris''. The genus is named after Gian Girolamo Zannichelli (1662–1729), Italian botanist.

Description

These slender plants grow submerged in water. The leaves are usually oppositely arranged and long and narrow. They have stipular sheaths. The flowers are unisexual. The male flowers have a single stamen with a slender filament and anthers that are 2-4- thecous. The female flowers have a cup-shaped membranous perianth. There are usually four carpels with a single pendulous ovule in each ovary. The stigma is shield shaped with toothed margins. The fruit is usually made of four long, dry achenes. The seeds are pendulous with a sub-cylindric embryo. The cotyledonous end is folded on itself twice.

Distribution

The species of this genus are widely distributed and are found growing in temperate and tropical regions around the world. They grow in brackish and salt water.

Selected species

The following species are accepted: *'' Zannichellia andina'' Holm-Niels. & R.R.Haynes *'' Zannichellia aschersoniana'' Graebn. *'' Zannichellia contorta'' (Desf.) Cham. *'' Zannichellia indica'' Rottler ex Royle, 1840 *'' Zannichellia obtusifolia'' Talavera, García-Mur. & H.Smit *'' Zannichellia palustris'' L. *'' Zannichellia pedicellata'' Buch.-Ham. ex Wall. *'' Zannichellia peltata'' Bertol. *'' Zannichellia tuberosa'' Lour.

References

* Potamogetonaceae Alismatales genera {{Alismatales-stub