Habit and leaf form. Shrubs; evergreen, or deciduous; bearing essential oils. Young stems cylindrical (often glandular verrucose). Mesophytic, or xerophytic. Leaves alternate; leathery, or ‘herbaceous’; shortly petiolate, or sessile; non-sheathing; gland-dotted (often glandular verrucose); aromatic; simple. Leaf blades dissected, or entire; when simple/dissected pinnatifid, or much-divided; pinnately veined, or one-veined. Leaves without stipules, or with stipules. Stipules when present, intrapetiolar; represented by glands. Leaves without a persistent basal meristem. Leaf anatomy. Hairs absent (lepidote trichomes present on young plants). Stem anatomy. Nodes unilacunar, or tri-lacunar. Secondary thickening developing from a conventional cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous.
Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; when solitary, terminal; in umbels. The terminal inflorescence unit cymose, or racemose. Inflorescences terminal. Flowers bracteate; bracteolate (bracteoles basal and insignificant); small to medium-sized; fragrant; regular, or somewhat irregular. The floral asymmetry when noticeable, involving the perianth and involving the androecium (not K). Flowers 5 merous; cyclic. Floral receptacle developing a gynophore (associated with the disk), or with neither androphore nor gynophore. Free hypanthium absent. Hypogynous disk absent (apparently). Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; gamosepalous; lobed; lepidote outside; imbricate; regular; with the median member posterior. Corolla 5; 1 -whorled; polypetalous; imbricate (the odd petal anterior); regular, or unequal but not bilabiate; lepidote outside; white, or yellow, or pink. Petals elliptic. Androecium 10. Androecial members unbranched, or branched (? by the splitting of simple primordia); free of the perianth; all equal, or markedly unequal; free of one another, or coherent (? the filaments usually more or less basally connate); 1 - adelphous, or 3–12 - adelphous; 1 -whorled, or 2 -whorled. Stamens 10; diplostemonous; alternisepalous. Filaments slender-terete. Anthers basifixed; versatile; dehiscing via longitudinal slits; introrse, or latrorse; tetrasporangiate; appendaged; glandular- apiculate. Gynoecium 5 carpelled (lepidote). The pistil when syncarpous, 5 celled. Gynoecium apocarpous, or syncarpous; eu-apocarpous, or semicarpous, or synstylous; superior. Carpel (when apo- or semicarpous) (1–)2–100 ovuled. Placentation of the free carpels marginal. Ovary unilocular, or plurilocular; when syncarpous, (1–)4–5(–100) locular. Styles 1, or 3–5; free, or partially joined; lateral (styles affixed to medial surface of inner margin of carpels, ovary with solid apex). Stigmas wet type, or dry type; papillate, or non-papillate; Group II type, or Group IV type. Placentation when syncarpous, axile. Ovules 1–5(–50) per locule; pendulous to ascending; epitropous; when two or more per cell, collateral, or superposed, or biseriate; arillate, or non-arillate; anatropous, or hemianatropous.
Fruit and seed features. Fruit fleshy, or non-fleshy; an aggregate, or not an aggregate. The fruiting carpels coalescing into a secondary syncarp, or not coalescing. The fruiting carpel dehiscent, or indehiscent; (when apocarpous) a follicle, or drupaceous, or baccate. Fruit a schizocarp (mericarps dehiscent). Mericarps when schizocarpic, comprising berrylets, or comprising follicles, or comprising nutlets, or comprising drupelets. Seeds oblong to reniform; endospermic, or non-endospermic. Embryo well differentiated. Cotyledons 2. Embryo chlorophyllous, or achlorophyllous; straight, or curved, or bent. Seedling. Germination phanerocotylar, or cryptocotylar.
Physiology, biochemistry. Aluminium accumulation not found. Photosynthetic pathway: C3.
Geography, cytology, number of species. A genus of 25 species.
Additional characters Petals uninerved.