Habit and leaf form. Herbs. Plants spiny (leaves of P. tanacetifolia with spiny hairs), or unarmed. Annual, or biennial, or perennial; plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves. Mesophytic. Leaves alternate; spiral; petiolate to subsessile; non-sheathing; without marked odour, or foetid; simple, or compound; when compound, pinnate. Leaf blades dissected; pinnatifid; pinnately veined, or palmately veined; cross-venulate. Leaves without stipules; without a persistent basal meristem. Leaf anatomy. Hairs present (usually), or absent. Stem anatomy. Nodes unilacunar. Secondary thickening developing from a conventional cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous; via hymenoptera.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in cymes. The terminal inflorescence unit cymose. Inflorescences terminal; initially coiled, straightening and elongating after anthesis, 1-sided, with 2 rows of flowers. Flowers regular; 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; gamosepalous (basally); imbricate; regular. Epicalyx absent. Corolla 5; 1 -whorled; appendiculate, or not appendiculate; gamopetalous; imbricate; campanulate to rotate; regular; blue, or white. Androecium 5. Androecial members adnate (to the corolla tube); all equal, or markedly unequal; free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 5. Staminal insertion near the base of the corolla tube. Stamens becoming exserted; isomerous with the perianth; oppositisepalous (alternating with the petals); all alternating with the corolla members. Filaments hairy (usually), or glabrous. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse; appendaged. Gynoecium 2 carpelled. The pistil 2 celled. Gynoecium syncarpous; synovarious to synstylovarious; superior, or partly inferior. Ovary plurilocular; 2 locular. Gynoecium median; stylate. Styles 1; forked (in the distal half); attenuate from the ovary; apical. Stigmas dry type; papillate; Group II type. Placentation axile. Ovules 5–20 per locule (i.e. ‘several’); funicled, or sessile; pendulous (when funicled); epitropous; non-arillate; anatropous, or amphitropous.
Fruit and seed features. Fruit non-fleshy; hairy; dehiscent; a capsule. Capsules loculicidal (via 2 valves). Seeds copiously endospermic. Endosperm oily. Cotyledons 2. Embryo straight. Seedling. Germination phanerocotylar.
Geography, cytology, number of species. Adventive. Australian states and territories: Western Australia. South-West Botanical Province.