Thunbergia Retz.

Scientific Description

Family Acanthaceae.

Habit and leaf form. Herbaceous climbers (without cystoliths). Perennial; plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves. Young stems obscurely tetragonal to cylindrical. Climbing; stem twiners. Twining anticlockwise. Hydrophytic, or helophytic, or mesophytic, or xerophytic. Leaves opposite; petiolate; gland-dotted, or not gland-dotted; simple. Leaf blades dissected, or entire; flat; pinnately veined, or palmately veined; cross-venulate. Leaves without stipules. Leaf blade margins entire. Stem anatomy. Nodes unilacunar. Secondary thickening anomalous; from a single cambial ring. Roots. Aerial roots present, or absent.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous. Pollination mechanism conspicuously specialized, or unspecialized.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, flowers paired in axils, usually combined into a terminal raceme. The terminal inflorescence unit cymose, or racemose. Flowers bracteate. Bracts intergrading with leaves. Flowers bi- bracteolate. Bracteoles often persistent, or deciduous (erect, enclosing calyx and corolla tube, free or connate along one hairy margin). Flowers somewhat irregular; zygomorphic. The floral asymmetry involving the perianth and involving the androecium. Flowers 5–20 merous; tetracyclic. Free hypanthium absent. Hypogynous disk present. Perianth with distinct calyx and corolla; 6–25; 2 -whorled; isomerous, or anisomerous. Calyx 5, or 8–20; 1 -whorled; gamosepalous; 8–20- lobed, or entire; hairy, or glabrous; unequal but not bilabiate (when lobes unequal), or regular; frequently nectariferous; when K5, with the median member posterior. Corolla 5; 1 -whorled; gamopetalous; contorted; tube constricted or not at base; unequal but not bilabiate (limb oblique with 5 subequal lobes). Androecium 4. Androecial members adnate; markedly unequal; free of one another, or coherent; 1 -whorled. Stamens 4; remaining included; didynamous; reduced in number relative to the adjacent perianth; oppositisepalous; all alternating with the corolla members. Anthers dorsifixed; dehiscing via longitudinal slits; bilocular; tetrasporangiate; appendaged (awned), or unappendaged. Pollen shed as single grains. Gynoecium 2 carpelled. The pistil 2 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary plurilocular; 2 locular. Gynoecium median. Ovary sessile. Styles 1; attenuate from the ovary; apical; much longer than the ovary at anthesis. Stigmas 1; 1 - lobed, or 2 - lobed; when simple, cup-shaped; wet type; papillate; Group III type. Placentation axile. Ovules 2 per locule; collateral; non-arillate, or arillate; hemianatropous, or anatropous, or campylotropous.

Fruit and seed features. Fruit non-fleshy (woody); dehiscent; a capsule (with expanded seed-bearing portion at base). Capsules loculicidal. Fruit elastically dehiscent. Dispersal unit the seed. Fruit 2–4 seeded. Seeds semi-globular; non-endospermic; small to medium sized; not conspicuously hairy. Embryo well differentiated. Cotyledons 2. Embryo achlorophyllous; curved. Seedling. Germination phanerocotylar.

Physiology, biochemistry. Aluminium accumulation not found.

Special features. The funicles not as in Acanthaceae.

Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, Northern Territory, and Queensland. Northern Botanical Province.

Additional characters Fruit apically long- rostrate. Pollen grains spiraperturate.