Rulingia R.Br.

Scientific Description

Family Sterculiaceae.

(Subfamily Byttnerioideae), Tribe Byttnerieae.

Habit and leaf form. Shrubs (with an indumentum of stellate hairs). To 0.3–4 m high. Mesophytic. Leaves small to medium-sized; alternate; petiolate; simple. Leaf blades dorsiventral; dissected, or entire; linear, or ovate, or obovate, or elliptic (or cordate); usually oblique at the base. Mature leaf blades adaxially pubescent, or glabrous (rarely); abaxially pubescent. Leaves with stipules (stipules narrow, the upper ones often laciniate). Stipules caducous. Leaf blade margins entire, or crenate, or dentate. Leaf anatomy. Hairs present, or absent; glandular hairs absent; complex hairs present. Complex hairs stellate.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’. Inflorescence few-flowered, or many-flowered. Flowers in cymes. Inflorescences terminal, or leaf-opposed, or axillary (rarely). Flowers pedicellate; bracteate. Bracts deciduous. Flowers small; regular. Floral receptacle with neither androphore nor gynophore. Perianth with distinct calyx and corolla; 10. Calyx present; 5; 1 -whorled; gamosepalous; lobed; lobulate (5-lobed); hairy (tomentose); valvate; more or less equalling the corolla, or exceeding the corolla; persistent; non-accrescent (not enclosing the fruit and shorter than the fruit). Epicalyx absent. Corolla present; 5 (broad, concave or convolute at the base, with a small broad or linear ligule at the top); 1 -whorled; polypetalous; glabrous abaxially; glabrous adaxially; white, or pink. Androecium present. Fertile stamens present. Androecium 10. Androecial members free of the perianth; coherent (connate: inner whorl of stamens shortly connate and alternating with the outer whorl of staminodes); 2 -whorled. Androecium including staminodes. Staminodes 5; petaloid (staminodes linear to narrowly ovate). Stamens 5; isomerous with the perianth; all opposite the corolla members. Anthers dehiscing via longitudinal slits; bilocular. Gynoecium 5 carpelled. The pistil 5 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary plurilocular; 5 locular; sessile. Gynoecium stylate. Styles 5; partially joined (partly connate at the top). Stigmas 5. Placentation axile. Ovules 2 per locule, or 3 per locule (rarely).

Fruit and seed features. Fruit 3–15 mm long; hairy (covered with long bristles or hairs); dehiscent; a capsule. Capsules loculicidal (by 5 valves). Dispersal unit the seed. Seeds 1 per locule, or 2 per locule.

Geography, cytology, number of species. World distribution: mainly Australia and Madagascar. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, South Australia, Northern Territory, and Queensland. Northern Botanical Province, Eremaean Botanical Province, and South-West Botanical Province. A genus of ca 20 species; 15 species in Western Australia.

Additional comments. Named after Dr Johann Philipp Rueling, a German botanist born in 1741.