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Alismataceae


This small family is widespread in tropical and temperate parts of both Hemispheres. In Australia, species of Alismataceae are found in freshwater marshes in all States.

Characteristic features of the family Alismataceae in Australia include:

  • marsh plants, usually with emergent, elliptic leaves with long petioles
  • leaf venation with many finer interveins connecting the main veins
  • flowers 3-partite, borne in branched panicles, the three inner perianth parts white or pinkish and petal-like
  • ovary comprising many free carpels, at maturity forming a fruit consisting of a dense, sometimes star-shaped cluster of follicles

Description

Annual or perennial aquatic or marsh herbs rooted in the substrate with their leaves emergent or rarely floating, perennating by corms, tubers, rhizomes or crowns. Vegetative reproduction absent or by corms, tubers or rhizomes. Internal secretions not obvious. Plants glabrous. Leaves alternate and spiral, all or mostly basal, petiolate. Stipule-like lobes absent. Lamina simple, symmetric, filiform, acicular, subulate, linear, lanceolate, ovate, elliptic or orbicular; base attenuate, rounded, cordate or hastate or sagittate; margins entire; venation palmate, or parallel, with the midrib conspicuous or inconspicuous, and the tertiary venation reticulate or not reticulate; herbaceous. Leaf ligule absent. Male and female flowers occurring on the same plant, or with bisexual flowers and male flowers occurring on the same plant, or with all the flowers bisexual. Inflorescences terminal; paniculate or verticillate. Bracts present. Flowers odourless; stalked. Floral disc absent; nectaries present on the receptacle or the carpels. Perianth regular, of 2 dissimilar whorls, imbricate in bud. Calyx segments free, of 3 sepals, herbaceous. Corolla segments free, of 3 petals, alternating with the calyx lobes, white, cream or pink, sometimes streaked, spotted, etc, membranous; lobes ±entire. Fertile stamens 6 or numerous, alternating with or opposite to the calyx segments, free of the corolla, free of the ovary and style, distinct from each other, all ±equal. Anthers basifixed, not versatile, opening outwards or sideways by longitudinal slits; 2-celled. Ovary superior and sessile. Carpels 360, free. Style terminal or eccentric, single and unbranched. Ovules 1 or 2 per locule, stalked or sessile; placentation basal. Fruit dry, usually indehiscent; a cluster of achenes (achenetum) or tardily dehiscent follicles (follicetum); the perianth on the maturing fruit deciduous or dry and persistent. Disseminule macro-surface featureless or winged, costate or with spines; micro-surface ±smooth, tuberculate or rugose, green or brown, dull. Seeds 1 or 2 per fruit. Aril absent. Cotyledons 1. Embryo curved.
(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 Alismataceae has not yet been published in the Flora of Australia. It will appear in Volume 39.

Australian genera of Alismataceae (as recognised for the Flora of Australia)

* = all species introduced

*Alisma
Caldesia
Damasonium
Limnophyton
*Sagittaria


Alisma plantago-aquatica (habit)
Photo: D.Hardin D.Hardin 


Caldesia acanthocarpa (fruits)
Photo: S.Jacobs S.Jacobs 


Caldesia oligococca (flowering plant)
Photo: S.Jacobs S.Jacobs 


Caldesia oligococca (flowers)
Photo: A.S.George A.S.George