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Genus Commersonia Family Malvaceae

Synonyms: Rulingia APNI*

Description: Trees or shrubs, prostrate to erect, stellate-tomentose. Stems, leaves and inflorescences with stellate hairs, and occasionally with intermixed clavate, glandular trichomes.

Leaves simple, ovate to broad-ovate, often cordate at base, glabrous to pubescent above, densely tomentose below, margins mostly irregularly toothed to ± entire, juvenile leaves initially trilobed, up to 6 times larger and with larger hairs than on mature leaves; petiolate; stipules early to late caducous,

Flowers bisexual, small, in cymose panicles, leaf-opposed or axillary. Calyx petaloid, 5-lobed. Petals 5, c. shorter than the calyx, with a broad base, incurved around stamens. Stamens 5, shortly united basally, opposite petals, filaments united in a short cup; staminodes 5, alternating with stamens, entire or deeply 3-lobed, central lobe wider than the 2 filiform lateral lobes. Ovary sessile, 5-locular, each loculus with 2–6 ovules; styles 5, glabrous, free (often twisted together) except at the fused, capitate stigmas.

Capsule opening into 5 valves, either glabrous or with a dense tomentum of stellate hairs, beneath reddish-brown setae (bristles), setae shaft glabrous to densely stellate hairy.

Distribution and occurrence: World: c. 58 species (Commersonia s. lat.), mainly tropical regions, South-East Asia, Australia & Pacific islands. Australia: 43 species (21 species in Commersonia s. str.; 22 species in Androcalva), all mainland States and the Northern Territory.

Occurs mainly inland in heathlands, shrublands, woodlands and rainforest, on various rocky substrates.

Recent molecular studies of the Malvaceae by CF Wilkins, BA Whitlock and other authors have concluded that the Rulingia is a synonym of Commersonia. Within Commersonia s. lat., two strongly supported clades (groups) were resolved; one group representing Commersonia s. str. (including Rulingia), the other described as the new genus Androcalva. In the treatment present here, a broad generic concept is applied such that all species are treated as species of Commersonia. However, each of the key leads that identify species that Wilkins et al. include in Androcalva are annotated.

For further reading links are provided to the following three papers: Polyphyly of Rulingia and Commersonia (Lasopetaleae, Malvaceae s.l.); A revision of Commersonia including Rulingia (Malvaceae s.l. or Byttneriacceae); A new Australian genus Androcalva separated from Commersonia (Malvaceae s.l. or Byttneriaceae).

Text by B.J. Conn (2013)
Taxon concept: Based in part on papers by CF Wilkins, BA Whitlock and others (2011), plus GP Guymer (Austrobaileya, volume 7)

 Key to the species 
NoteCouplets 9–12 of this key identify those species of Commersonia that have also been recognised as the separate genus Androcalva9
1Anthers more or less laterally dehiscent; staminodes densely hairy; hairs stellate (Commersonia s. str.)2
Anthers extrorsely dehiscent; staminodes glabrous (Androcalva)9
2Staminodes 3 between each stamen; tree (shrub-like when juvenile or regrowth form); inflorescence with 50–200 flowers; flowers cream-colouredCommersonia bartramia
Staminodes 1 between each stamen; shrubs; inflorescence with 1 to many flowers; flowers white, pink or yellow
                       Back to 1
3Upper surface of leaf with few, scattered hairs towards margin or glabrous throughout4
Upper surface of leaf moderately to very densely hairy
                       Back to 2
4Leaf elliptic to narrowly elliptic, chartaceous; petioles less than 5 mm long; shrub, prostrate, becoming procumbent; fruit with setae up to 0.9 mm longCommersonia hermanniifolia
Leaf ovate, thin pliable; petioles 10–20 mm long; prostrate mat; fruit with setae more than 2 mm long. (NSW: N of Newcastle to Vic: Gippsland Lakes)
                       Back to 3
Commersonia prostrata
5Petal base prominently gibbous (cup-like) below and above petal attachment pointCommersonia amystia
Petal base not gibbous, or gibbous only above petal attachment point
                       Back to 3
6Lower surface of leaf densely hairy; hairs long, stellate, all equally long, epithelium just visible; fruit setae have apical hairs with reflexed armsCommersonia dasyphylla
Lower surface of leaf tomentose with long, stellate hairs, above dense, short-armed, stellate hairs, epithelium not visible; fruit setae have apical hairs with erect or horizontal arms
                       Back to 5
7Leaf narrowly ovate; margin mainly entire; petals absent or less than 3 mm long; ligule up to 1.7 mm longCommersonia salviifolia
Leaf ovate or elliptic; margin serrulate; petals 2.1–3.8 mm long; ligule 1.3–2.9 mm long
                       Back to 6
8Mature leaves ovate or narrowly ovate; anther filaments mainly stellate hairy; fruit with setae dense throughout, up to 4.6 mm longCommersonia rugosa
Mature leaves narrowly elliptic or elliptic, rarely ovate; anther filaments mainly glabrous; fruit with setae scattered towards apex, up to 0.9 mm long
                       Back to 7
Commersonia breviseta
9Staminodes three between each stamen, all narrowly spathulate, petaloid, glabrous; leaf with apex acute; pedicels articulated; capsules with conspicuous, triangular wings10
Staminodes 1–3 between each stamen, with central or single staminode petaloid, ovate or narrowly triangular; lateral staminodes (when present) terete,linear or clavate and apical third minutely papillose; leaf with apex obtuse to subacute; pedicels not articulated; capsules lacking conspicuous wings
                       Back to 1
10Stems and pedicels with conspicuous, red-tipped, clavate, glandular trichomes, much longer than stellate hairsCommersonia viscidula
Stems and pedicels without glandular trichomes, or glandular trichomes inconspicuous and shorter than, or as long as stellate hairs
                       Back to 9
11Stem and flowering stems with white, stellate hairs, or hairs white with pale brown centres, c. 0.5 mm longCommersonia fraseri
Stem and flowering stems with long golden to ferruginous stellate hairs, c. 1 mm long
                       Back to 10
Commersonia rossii
12Petals with ligule narrower at apex than at base, either narrowly triangular, triangular, ovate or narrowly ovate with apex blunt, or narrowly oblong with base only very slightly broader base. Petal base (when lateral lobes flattened) 2–4.5mm acrossCommersonia rosea
Petal with ligule broader towards apex than base, orbicular, suborbicular, obovate, spathulate; petal base (when flattened) less than 2.5 mm wide
                       Back to 9
Commersonia procumbens

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