Brunoniella Bremek.

Scientific Description

Family Acanthaceae.

Habit and leaf form. Small, prostrate or erect herbs (with cystoliths). Perennial; plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves. Young stems angled. Hydrophytic, or helophytic, or mesophytic, or xerophytic. Leaves opposite; gland-dotted, or not gland-dotted; simple. Leaf blades entire; flat; pinnately veined, or palmately veined; cross-venulate. Leaves without stipules. Leaf blade margins entire. Stem anatomy. Nodes unilacunar. Secondary thickening developing from a conventional 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’. The terminal inflorescence unit cymose, or racemose. Inflorescences axillary (usually); cymose, spicate or of sessile clusters; pseudanthial, or not pseudanthial. Flowers bracteate (usually intergrading with leaves); bi- bracteolate. Bracteoles shorter than calyx. Flowers regular; 5 merous; tetracyclic. Free hypanthium absent. Hypogynous disk present; annular (with irregular margin, inconspicuous). Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; gamosepalous; lobed; regular (equal); with the median member posterior. Corolla 5; 1 -whorled; gamopetalous (at least basally); imbricate, or contorted, or with open aestivation; funnel-shaped; regular. Androecium 4 (usually), or 3–6 (in cleistogamous flowers of B. australis). Androecial members adnate; markedly unequal; free of one another, or coherent; 1 -whorled. Stamens (3–)4(–6). Staminal insertion near the base of the corolla tube. Stamens remaining included; didynamous; reduced in number relative to the adjacent perianth, or isomerous with the perianth; oppositisepalous; all alternating with the corolla members. Anthers dorsifixed; dehiscing via longitudinal slits; bilocular; tetrasporangiate; 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; 2 - lobed (lobes equal or unequal); dry type; minutely hairy; Group II type. Placentation axile. Ovules 5–10 per locule; superposed; non-arillate, or arillate; hemianatropous, or anatropous, or campylotropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule (flattened, cylindrical or ellipsoid). Capsules loculicidal. Fruit elastically dehiscent. Dispersal unit the seed. Fruit 1–12 seeded (often not all ovules developing into seed). Seeds discoid to ellipsoid, with acute apex; non-endospermic; conspicuously hairy (hairs expanding when wet). Embryo well differentiated. Cotyledons 2. Embryo achlorophyllous; curved. Seedling. Germination phanerocotylar.

Physiology, biochemistry. Aluminium accumulation not found.

Special features. The seeds on elongated, indurated, hook-shaped funicles (‘retinacula’).

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