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This small family of a few species of fresh and brackish-water aquatic plants is almost cosmopolitan, though more common in the Southern Hemisphere. In Australia, plants in this family occur in fresh and saline, still waterbodies and on mudflats along quiet coastlines, around the southern and eastern coastlines and near-coastal areas.
Characteristic features of the family Zannichelliaceae in Australia include: - annual or short-lived, mat-forming, submerged aquatics, with alternate leaves which are often very fine, the leaves sheathing the stem and often 2-lobed at the junction of blade and sheath
- flowers very small and more or less enclosed in the upper sheaths
- female flower of several free carpels each with a terminal style expanded at its apex; male flowers comprising a large, stalked, 6-celled anther
- fruit small and hard
Description
Annual or perennial, freshwater, brackish or marine aquatic
herbs rooted in the substrate with their leaves all or mostly submerged.
Perennating by rhizomes. Vegetative reproduction by rhizomes. Internal
secretions not obvious. Plants glabrous. Leaves alternate and spiral,
or distichous, or apparently opposite, cauline, sessile. Stipule-like
lobes absent. Lamina simple, symmetric, filiform, acicular, subulate or
linear; base truncate, lobed or auriculate; margins entire or serrate,
±flat; one-veined, with the midrib conspicuous or inconspicuous,
and the tertiary venation not reticulate; surfaces not punctate; herbaceous.
Leaf ligule present or absent. Male and female flowers occurring on the
same or on separate plants, or with all the flowers bisexual. Inflorescences
terminal or axillary, consisting of glomerules, dichasial cymes or solitary
flowers. Spathes present or absent. Bracts present or absent. Pollination
by water. Flowers odourless, sessile or stalked. Perianth regular, of
1 vestigial whorl, with 3 fused lobes, or absent, bell-shaped, or fused
shortly at base, without contrasting markings, membranous. Fertile stamens
1–3 or 6, not clearly correlated with and free of the perianth, free of
the ovary and style, fused by their anthers, all ±equal. Staminal
filaments absent. Anthers not versatile, opening outwards by longitudinal
slits; 1–2 or more than 4-celled. Ovary superior and sessile. Carpels
3, free or fused; ovary with 3 locules. Style terminal, branching from
the base. Ovules 1 per locule, sessile; placentation apical or marginal.
Fruit dry, indehiscent, a cluster of achenes (achenetum) or druplets?;
the perianth on the maturing fruit deciduous, or persistent. Disseminule
micro-surface ±smooth, tuberculate, verrucose or rugose, yellow,
brown, grey or black, dull. Seed 1 per fruit. Aril absent. Cotyledons
1. Embryo straight, curved or coiled.
(Note: this description has been generated from the coded data compiled for the key. Any errors in the key data will be reflected in the descriptions.)
A treatment of the family Zannichelliaceae has not yet been published in the Flora of Australia. It will appear in Volume 30.
Australian genera of Zannichelliaceae (as recognised for the Flora of Australia)
Lepilaena Zannichellia
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Zannichellia ?palustris (fruits)
Photo: S.Jacobs © S.Jacobs
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Zannichellia ?palustris (habit)
Photo: S.Jacobs © S.Jacobs
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