Habit and leaf form. Herbs. Annual, or perennial. Young stems cylindrical, or tetragonal. Hydrophytic, or helophytic. Leaves alternate (rarely), or opposite, or whorled; decussate; 3–8 per whorl; petiolate (rare), or subsessile, or sessile; gland-dotted, or not gland-dotted; simple. Leaf blades entire; elliptic, or oblong, or ovate, or linear, or orbicular; pinnately veined; cross-venulate; cordate, or cuneate at the base. Leaves without stipules. Leaf blade margins entire. Leaves 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. Plants homostylous, or heterostylous. Entomophilous.
Inflorescence and flower features. Flowers solitary; axillary; sessile to subsessile; bracteate, or ebracteate (rarely); bracteolate; minute to medium-sized; usually regular; 3–6 merous; pentacyclic. Floral receptacle developing an androphore, or with neither androphore nor gynophore. Free hypanthium present; campanulate, or urceolate, or globose; usually membranous and translucent; sinus appendages 3–5 or absent; nectary glands often present at base. Hypogynous disk present, or absent. Perianth with distinct calyx and corolla; (3–)8–16(–32); 2 -whorled; isomerous. Calyx present; 3–6; 1 -whorled; gamosepalous; blunt-lobed; lobes valvate; tubular, or campanulate, or urceolate; unequal but not bilabiate, or regular; persistent. Epicalyx present, or absent. Corolla present, or absent; 3–6; 1 -whorled; polypetalous; plicate; unequal but not bilabiate, or regular; red, or purple, or orange. Petals elliptic, or oblong, or obovate; clawed, or sessile. Androecial members definite in number. Androecium 1–6. Androecial sequence determinable, or not determinable. Androecial members when determinable, maturing centripetally; adnate (to the hypanthium, low down); all equal, or markedly unequal; free of one another; 1–3 -whorled (or several). Androecium exclusively of fertile stamens, or including staminodes (occasionally some stamens reduced to staminodes). Stamens 1–6; attached inside the hypanthium; reduced in number relative to the adjacent perianth to isomerous with the perianth to polystemonous; oppositisepalous; inflexed in bud, or erect in bud. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Gynoecium 2–4 carpelled. The pistil 1 celled, or 2–4 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary incompletely plurilocular; incompletely 2–4 locular; shortly stipitate, or sessile. Gynoecium non-stylate, or stylate. Styles 1; apical. Stigmas 1; usually capitate. Placentation axile. Ovules (1–)5–50 per locule; ascending, or horizontal; non-arillate; anatropous.
Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules septicidal (by valves). Seeds non-endospermic; wingless. Cotyledons 2. Embryo straight.
Etymology. From the Latin for "wheel" and the diminutive suffux -al-; the leaves of the original species R. verticillatus are verticillate (arranged in a whorl).
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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/