Sebaea R.Br.

Scientific Description

Common name. Sebaeas. Family Gentianaceae.

Habit and leaf form. Herbs. Annual. Leaves cauline. To 0.015–0.25 m high. Mesophytic. Not heterophyllous. Leaves small; not fasciculate; opposite; decussate; not decurrent on the stems; ‘herbaceous’; not imbricate; sessile; simple; epulvinate. Leaf blades dorsiventral; entire; broadly ovate. Mature leaf blades adaxially glabrous; abaxially glabrous. Leaves without stipules. Leaf blade margins entire. Leaves without a persistent basal meristem. Leaf anatomy. Hairs absent. Roots. Aerial roots absent.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Plants homostylous. Floral nectaries absent. Entomophilous.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; not crowded at the stem bases. Inflorescence few-flowered. Flowers in cymes. The terminal inflorescence unit cymose. Inflorescences a 2–4 branched dichasium. Flowers pedicellate (below), or sessile (above); small; regular; 4 merous, or 5 merous; tetracyclic. Free hypanthium absent. Perianth with distinct calyx and corolla; 8, or 10; 2 -whorled; isomerous. Calyx present; 4, or 5; 1 -whorled; gamosepalous; lobed; lobulate. Calyx lobes markedly longer than the tube. Calyx at apex erect, or spreading; hairy (papillose or scabrid on the keels); usually imbricate; exceeded by the corolla; regular; green; persistent. Calyx lobes oblong, or ovate. Corolla present; 4, or 5; 1 -whorled; gamopetalous; lobed; lobulate. Corolla lobes markedly shorter than the tube. Corolla contorted; rotate, or urceolate; regular; glabrous abaxially; glabrous adaxially; plain; creamy white, or yellow; persistent. Corolla lobes broadly oblong, or orbicular (or broadly lanceolate). Corolla members entire. Androecial members definite in number. Androecium 4, or 5. Androecial members adnate (to the corolla tube); all equal; free of one another; 1 -whorled. Stamens 4, or 5. Staminal insertion near the base of the corolla tube. Stamens all inserted at the same level; becoming exserted, or remaining included; all more or less similar in shape; isomerous with the perianth; all alternating with the corolla members; erect in bud. Filaments filiform. Anthers all alike; basifixed; non-versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged, or unappendaged. The anther appendages apical, or basal. Fertile gynoecium present. Gynoecium 2 carpelled. The pistil 2 celled. Gynoecium syncarpous; synstylovarious; superior. Ovary plurilocular; 2 locular. Gynoecium median; stylate. Styles 1; attenuate from the ovary; apical; becoming exserted, or not becoming exserted (sometimes with a middle or basal swelling); deciduous; hairless. Stigmas 2; clavate, or capitate.

Fruit and seed features. Fruit to c. 4 mm long; non-fleshy; not hairy; dehiscent; a capsule. Capsules septicidal. Dispersal unit the seed. Fruit 30–50 seeded (‘many’). Seeds endospermic; minute. Cotyledons 2. Embryo straight.

Geography, cytology, number of species. World distribution: paleotropic. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia, South Australia, Queensland, New South Wales, Victoria, Australian Capital Territory, and Tasmania. South-West Botanical Province. 2n = c. 54 in S. ovata. A genus of c. 100 species; 1 species in Western Australia; 0 endemic to Western Australia.

Etymology. After Albertus Seba (1665–1736), apothecary of Amsterdam, traveller and naturalist.