Habit and leaf form. Herbs; bearing essential oils. Annual, or perennial. Leaves basal and cauline. Mesophytic, or xerophytic. Leaves alternate, or opposite; petiolate; non-sheathing; gland-dotted, or not gland-dotted; aromatic (via capitate glands), or without marked odour; simple. Leaf blades dissected (or lobed); pinnately veined, or palmately veined. Leaves with stipules. Stipules interpetiolar, or intrapetiolar; leafy (or membranous). Leaves without a persistent basal meristem. Leaf anatomy. Hairs present (with loose, spreading or appressed hairs). Stem anatomy. Nodes tri-lacunar. Secondary thickening absent, or developing from a conventional cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present. Nectar secretion from glands at the base of the ante-sepal stamens.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’ (paired), or solitary (very rarely). Inflorescences terminal; with involucral bracts, or without involucral bracts. Flowers pedicellate; bracteolate; small, or medium-sized; regular; 5 merous; cyclic. Free hypanthium absent. Hypogynous disk present; of separate members (alternating with C, around A). Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; polysepalous, or gamosepalous; imbricate (with valvate tips); regular; neither appendaged nor spurred; persistent; with the median member posterior. Corolla 5; 1 -whorled; polypetalous; imbricate; regular; pink to purple; deciduous (caducous). Petals obovate; clawed. Corolla members bilobed, or entire. Androecium 10. Androecial sequence determinable. Androecial members all equal to markedly unequal; free of one another, or coherent (basally); when coherent, 1 - adelphous; 2 -whorled. Stamens 10; diplostemonous; alternisepalous (obdiplostemonous). Filaments hairy (margins only); narrowly ovate. Anthers oblong to circular in outline; dorsifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Gynoecium 5 carpelled. The pistil 5 celled. Gynoecium syncarpous; synstylovarious; superior. Ovary plurilocular; 5 locular. Styles 1 (with an elongating, persistent column); attenuate from the ovary; apical. Stigmas 5; dry type; papillate; Group II type. Placentation axile. Ovules 2 per locule; ascending; epitropous; with ventral raphe; superposed; anatropous to campylotropous.
Fruit and seed features. Fruit non-fleshy; a schizocarp. Mericarps 5; ovoid; awns hairy on the outer surface with minute glandular hairs, almost glabrous on the inner surface, breaking away elastically from the base and curling upwards at maturity, remaining attached at the apex, not twisting. Seeds 1 per mericarp. Seeds more or less ellipsoid to globular; endospermic (scantily), or non-endospermic; exotegmic. Cotyledons 2. Embryo straight, or curved to bent. Seedling. Germination phanerocotylar.
Geography, cytology, number of species. Native of Australia. Not endemic to Australia.