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Zannichelliaceae


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 13 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; 12 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


Zannichellia ?palustris (fruits)
Photo: S.Jacobs S.Jacobs 


Zannichellia ?palustris (habit)
Photo: S.Jacobs S.Jacobs