Habit and leaf form. Shrubs; evergreen; bearing essential oils. Plants with neither basal nor terminal concentrations of leaves; to 0.2–1.3 m high. Leptocaul. Mesophytic. Leaves minute to small; opposite; ‘herbaceous’, or leathery; petiolate to sessile; gland-dotted; aromatic; edgewise to the stem, or with ‘normal’ orientation; simple; epulvinate. Leaf blades dorsiventral, or isobilateral, or centric; entire; flat, or solid; semi-terete; linear, or lanceolate, or oblong, or ovate; linear, or ovate, or obovate, or oblong, or elliptic, or orbicular; pinnately veined, or parallel-veined, or one-veined; cross-venulate, or without cross-venules. Mature leaf blades adaxially glabrous, or pubescent (on margins); abaxially glabrous, or pubescent (on margins). Leaves without stipules; without a persistent basal meristem. Stem anatomy. Secondary thickening developing from a conventional cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous, or ornithophilous. Pollination mechanism unspecialized.
Inflorescence and flower features. Flowers solitary (apparently), or aggregated in ‘inflorescences’; axillary. Inflorescences axillary; commonly a ‘monad’ with a very short peduncle and a relatively long anthopodium; metaxytriads occurring rarely in R. dimorphandra which usually has dichasia, the two flowers of which appear to be at different stages of development. Flowers (bi) bracteolate. Bracteoles persistent. Flowers minute to medium-sized; regular, or somewhat irregular. The floral asymmetry (when noticeable) involving the androecium. Flowers 5(–6) merous; cyclic. Free hypanthium present (petals ‘inserted on the calyx’); campanulate, or obconic, or tubular (to hemispherical); extending beyond ovary. Hypogynous disk present (lining the hypanthium). Perianth with distinct calyx and corolla; 10, or 12; 2 -whorled; isomerous. Calyx present; 5(–6); 1 -whorled; gamosepalous; lobed. Calyx lobes markedly shorter than the tube, or about the same length as the tube. Calyx erect to spreading; imbricate, or valvate; exceeded by the corolla; regular; persistent. Calyx lobes oblong, or triangular (to hemispherical). Corolla present; 5(–6); 1 -whorled; polypetalous; imbricate; regular; white, or pink. Petals obovate, or orbicular; clawed. Androecial members definite in number. Androecium (5–)10(–12). Androecial members unbranched. Androecial sequence determinable, or not determinable. Androecial members free of the perianth, or adnate (to petal claws); all equal (when only 5 present), or markedly unequal (the antepetalous broader and longer than the antesepalous stamens); free of one another (? when only five present), or coherent (the filaments fused to varying extents, from shortly near the base to almost their whole length); 1 - adelphous; 2 -whorled (if considered as separate antesepalous and antepetalous whorls), or 1 -whorled (apparently). Androecium exclusively of fertile stamens, or including staminodes (hair-like processes at the base of the antepetalous filaments of some species). Stamens 5–12; attached on the rim of the hypanthium, or attached above the hypanthium; becoming exserted, or remaining included; not didynamous, not tetradynamous; all more or less similar in shape (when only 5), or distinctly dissimilar in shape (usually); isomerous with the perianth, or diplostemonous, or irregular in those species where some of the antesepalous stamens are missing, or some of the antepetalous stamens are doubled; oppositisepalous, or alternisepalous and oppositisepalous; both opposite and alternating with the corolla members, or all alternating with the corolla members; erect in bud, or inflexed in bud. Filaments not geniculate; broadly strap-shaped. Anthers separate from one another; all alike; dorsifixed (in R. carnosa, the anthers of all other species attached (but only at the midpoint) to the adaxial surface of the filament); non-versatile (usually), or versatile (in R. carnosa); dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged (? the connective with a globular to obovoid gland), or unappendaged. Gynoecium 3(–4) carpelled. The pistil 3(–4) celled. Gynoecium syncarpous; eu-syncarpous; partly inferior. Ovary plurilocular; 3(–4) locular. Epigynous disk absent. Gynoecium stylate. Styles 1; simple; from a depression at the top of the ovary; apical. Stigmas 1; capitate. Placentation axile (placentae not stalked). Ovules 2–12 per locule; ascending; collateral, or biseriate (rows interlocking, or rarely almost radially arranged); non-arillate; anatropous.
Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules dehiscing by valves, opening widely until almost at right angles to the fruit axis. Seeds reniform; non-endospermic; small; arillate, or non-arillate. Cotyledons 2. Embryo consisting of a large radicle with small cotyledons on a slender neck. Testa crustaceous, smooth to papillose.
Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia. South-West Botanical Province.
Etymology. After Sebastian Rinz and his son, Jacob, horticulturists of Frankfurt, who introduced many exotic plants into Germany in the early 19th century.
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Western Australian Herbarium (1998–). FloraBase—the Western Australian Flora. Department of Biodiversity, Conservation and Attractions. https://florabase.dpaw.wa.gov.au/