Xanthosia Rudge

Scientific Description

Family Apiaceae.

Habit and leaf form. Herbs, or shrubs; bearing essential oils, or without essential oils (?); resinous, or not resinous (?). Plants unarmed. Herbs perennial; plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves. Helophytic, or mesophytic. Leaves small to medium-sized; alternate; ‘herbaceous’, or leathery; petiolate; gland-dotted, or not gland-dotted (?); aromatic, or foetid, or without marked odour (?); simple, or compound; pulvinate, or epulvinate (?); when compound ternate. Leaf blades when simple entire, or dissected; flat; when simple/dissected, 3-lobed or repeatedly ternately divided; pinnately veined. Leaves without stipules. Leaf blade margins entire, or dentate. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present, or 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. Unisexual flowers absent. Plants hermaphrodite. Entomophilous.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’ (usually), or solitary; in umbels. Inflorescences simple, or compound. The terminal inflorescence unit cymose, or racemose (?). Inflorescences terminal, or leaf-opposed; usually with 2–4 short rays and 1 or more flowers in the centre between the rays, umbellules with 1 or more ray bracts; with involucral bracts; pseudanthial (when bracts or ray bracts petal-like), or not pseudanthial. Flowers pedicellate, or sessile; bracteate; small; regular to somewhat irregular (?); 5 merous (except for the gynoecium); cyclic; tetracyclic. Free hypanthium absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous; white, or green to yellow. Calyx 5; 1 -whorled; gamosepalous; lobed (lobes similar in length to petals); persistent. Corolla 5; 1 -whorled; polypetalous; valvate; unequal but not bilabiate, or regular (?); white, or green to yellow. Corolla members entire (apex narrow). 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 circular in outline; dehiscing via longitudinal slits; introrse; tetrasporangiate. 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 2-lobed 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; hairy, or not hairy; a schizocarp. Mericarps 2 (with 5–9 ribs and rounded outer margin). 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. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia, South Australia, Queensland, New South Wales, Victoria, Australian Capital Territory, and Tasmania.

Additional characters Petals inflexed.