Hydrocotyle L.

Scientific Description

Family Apiaceae.

Habit and leaf form. Small, erect to prostrate herbs; bearing essential oils, or without essential oils (?); resinous, or not resinous (?). Annual, or perennial; plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves (?); rooting at nodes. Hydrophytic, or helophytic, or mesophytic. Leaves small to large; alternate; ‘herbaceous’; petiolate; more or less sheathing. Leaf sheaths with free margins. Leaves gland-dotted, or not gland-dotted (?); aromatic, or foetid, or without marked odour (?); simple, or compound; peltate, or not peltate; pulvinate, or epulvinate (?); when compound, palmately divided with 3–5 entire to lobed leaflets. Leaf blades when simple entire, or dissected; flat; when entire, orbicular (or reniform or cordate); palmately veined. Leaves with stipules. Stipules translucent, entire or laciniate. Leaf blade margins entire, or crenate, or serrate, 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 (usually), or functionally male, or functionally female. Unisexual flowers absent (usually), or present. Plants hermaphrodite (usually), or dioecious. Entomophilous.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in umbels, or in heads, or in spikes. Inflorescences simple, or compound (rarely). The terminal inflorescence unit cymose, or racemose (?). Inflorescences terminal; usually pedunculate; with involucral bracts, or without involucral bracts. Flowers shortly pedicellate (usually); bracteate, or ebracteate. Bracts when present, very small. Flowers small; regular to somewhat irregular (?); 5 merous (except for the gynoecium); cyclic; tetracyclic, or tricyclic. Free hypanthium absent. Perianth with distinct calyx and corolla (but the calyx lobes minute and inconspicuous), or petaline; 5, or 10; 2 -whorled, or 1 -whorled; isomerous; green to white, or purple. Calyx present to vestigial, or absent; when detectable, 5; 1 -whorled; gamosepalous. Corolla 5; 1 -whorled; polypetalous; valvate; unequal but not bilabiate, or regular; green to white, or purple. Petals ovate. Corolla members acute. Fertile stamens present, or absent (female and sterile flowers). 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. Fertile gynoecium present, or absent (male and sterile 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 disc-like 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 (usually more or less distinctly 5-ribbed, smooth or sculptured). 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. Not endemic to Australia. Australian states and territories: Western Australia, South Australia, Northern Territory, Queensland, New South Wales, Victoria, Australian Capital Territory, and Tasmania.

Additional characters Petals not inflexed.