Habit and leaf form. Erect herbs (with a fleshy taproot and spotted stems); bearing essential oils, or without essential oils (?); resinous, or not resinous (?). Annual, or biennial; plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves (?). Stem internodes hollow. Helophytic, or mesophytic. Leaves medium-sized to very large; alternate; ‘herbaceous’; petiolate; more or less sheathing. Leaf sheaths with free margins. Leaves gland-dotted, or not gland-dotted; foetid (acrid-smelling when crushed); compound; not peltate; pulvinate, or epulvinate; bipinnate, or multiply compound (3–4-pinnate). Leaf blades pinnately veined. Leaves without stipules. Leaf blade margins dentate. Leaves without a persistent basal meristem. Leaf anatomy. Hairs absent. Stem anatomy. Nodes multilacunar, or tri-lacunar (?). Secondary thickening developing from a conventional cambial ring, or anomalous (?); from a single cambial ring.
Reproductive type, pollination. Fertile flowers hermaphrodite, or hermaphrodite and functionally male (often together in the same umbel). Unisexual flowers present, or absent. Plants hermaphrodite, or andromonoecious. Entomophilous.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in umbels. Inflorescences compound. The terminal inflorescence unit cymose, or racemose (?). Inflorescences terminal; rays stiff. Flowers bracteate. Bracts ovate or linear. Flowers bracteolate. Bracteoles ovate or linear. Flowers small; regular to somewhat irregular. The floral asymmetry involving the perianth (the corolla only). Flowers 5 merous (except for the gynoecium); cyclic; tricyclic. Free hypanthium absent. Perianth petaline; 5; 1 -whorled; white. Corolla 5; 1 -whorled; polypetalous; valvate; regular to unequal but not bilabiate (subequal); white. Petals broadly obovate. Corolla members entire. Androecium 5. Androecial members free of the perianth; all equal to markedly unequal (?); free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 5; isomerous with the perianth; oppositisepalous; inflexed in bud. Anthers narrowly ovate in outline; dehiscing via longitudinal slits; introrse; tetrasporangiate. Fertile gynoecium present, or absent (male flowers). Gynoecium 2 carpelled. The pistil 2 celled. Gynoecium syncarpous; synovarious; inferior. Ovary plurilocular; 2 locular. Gynoecium median. Epigynous disk present. Gynoecium stylate. Styles 2; free to partially joined (their bases thickened into a flat stylopodium crowning the ovary); apical. Stigmas wet type; non-papillate; Group IV type. Placentation axile, or apical (?). Ovules 1 per locule, or 2 per locule (usually two, but one abortive ?); pendulous; epitropous; non-arillate; anatropous.
Fruit and seed features. Fruit non-fleshy; not hairy; a schizocarp. Mericarps 2 (5-ribbed, secondary ribs absent). Seeds endospermic. Endosperm oily. Embryo well differentiated. Cotyledons 2. Embryo achlorophyllous; straight. Seedling. Germination phanerocotylar.
Physiology, biochemistry. Aluminium accumulation not found. Photosynthetic pathway: C3.
Geography, cytology, number of species. Adventive. Australian states and territories: Western Australia, South Australia, Queensland, New South Wales, Victoria, Australian Capital Territory, and Tasmania.
Economic uses, etc. Highly toxic weed due to the presence of alkaloids.
Additional characters Petals inflexed.