Families of Flowering Plants of Australia

Idiospermaceae

This primitive family comprises a single species, Idiospermum australiensis, found in lowland rainforests near Cairns in north-east Queensland.

Characteristic features of the family Idiospermaceae in Australia include:

tree with opposite, simple, entire leaves
flowers bisexual, borne singly in leaf axils, with 30-40 spirally-arranged, rather thick, greenish, red or purplish perianth parts and up to 15 similar but smaller stamens
ovary comprising a single carpel inside a hollow, cup-shaped receptacle
fruits large, fleshy, with 1 or 2 large seeds each with 3 or 4 fleshy cotyledons

Description

Evergreen trees. Internal secretions not obvious. Plants glabrous, or with simple, non-glandular, unicellular hairs. Leaves opposite, petiolate. Stipules absent. Lamina simple, symmetric, lanceolate, ovate, elliptic or oblong; base cuneate or attenuate; margins entire, ±flat; venation pinnate, with the midrib conspicuous, and the tertiary venation reticulate; surfaces not punctate; leathery. All the flowers bisexual. Inflorescences terminal, consisting of racemes, cymes or solitary flowers. Bracts present. Pollination by insects. Flowers odourless or fragrant, stalked. Floral disc absent. Free hypanthium ±present. Perianth regular, of 1 whorl only or all whorls ±similar, with 30–40, free, petaloid segments, imbricate in bud, cream, pink, red (and?) purple, without contrasting markings; inner perianth parts herbaceous or papery. Fertile stamens 13–15, not clearly correlated with and free of the perianth segments, free of the ovary and style, distinct from each other, all ±equal. Staminodes present. Staminal filaments distinctly flattened, leaf-like or petaloid, with embedded anther-sacs. Anthers not versatile, opening outwards by longitudinal slits, 4-celled; appendages apical. Ovary part-inferior. Carpels 1 (–2), free from each other. Style terminal, single and unbranched. Ovules 1 (–2), sessile; placentation basal. Fruit a fleshy, indehiscent pome; the perianth on the maturing fruit deciduous. Disseminule micro-surface ±smooth, green or brown and ?dull. Seeds 1 per fruit. Aril present or absent. Cotyledons 3 or 4. Embryo round and shapeless.
(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 Idiospermaceae has not yet been published in the Flora of Australia. It will appear in Volume 2.

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

Idiospermum