Sphenocleaceae

This is a very small family of only a few species, perhaps originally native to tropical Africa. One species is a widespread weed of wet places such as rice paddies and marshes almost throughout the tropics, including northern Australia.

Characteristic features of the family Sphenocleaceae in Australia include:

• annual, erect marsh herbs with hollow, succulent stems and alternate leaves
  
• flowers small, regular, in dense, terminal spikes
  
• petals, sepals and stamens 5, the petals fused into a short bell-shaped tube
  
• ovary inferior (or partly so), developing into a membranous capsule that splits around its circumference to release the small seeds

Description

Annual terrestrial herbs. Stem internodes solid or hollow. Internal secretions not obvious. Plants glabrous. Leaves alternate and spiral, cauline, petiolate. Stipules absent. Lamina simple, symmetric, lanceolate, ovate or oblong; base cuneate or attenuate; margins entire; ±flat; one-veined, or the venation pinnate, with the midrib conspicuous, and the tertiary venation not reticulate; surfaces not punctate; herbaceous or succulent. All the flowers bisexual. Inflorescences terminal, consisting of spikes. Bracts and bracteoles present. Pollination by insects. Flowers odourless, sessile. Perianth regular, of 2 dissimilar whorls, imbricate in bud. Calyx segments fused, with 5 lobes; calyx cup-shaped, herbaceous. Corolla segments fused, with 5 lobes, alternating with the calyx lobes; corolla bell-shaped or urn-shaped, white, cream or yellow, without contrasting markings, membranous; lobes ±entire. Fertile stamens 5, opposite to the calyx lobes, at least partly fused to the corolla, free of the ovary and style, distinct from each other, all ±equal. Anthers dorsifixed, versatile, opening inwards by longitudinal slits, 2-celled. Ovary part-inferior. Carpels 2, fused; ovary with 2 locules. Style terminal, single and unbranched and the stigma capitate. Ovules numerous per locule, sessile; placentation axile. Fruit a dry dehiscent circumscissile capsule; the perianth on the maturing fruit deciduous, or dry and persistent. Disseminule micro-surface rugose, yellow or brown, glossy. Seeds numerous per fruit. Aril absent. Cotyledons 2. Embryo straight.
(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 Sphenocleaceae has not yet been published in the Flora of Australia. It will appear in Volume 34.

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

Sphenoclea