Xenostegia D.F.Austin & Staples

Brittonia 32:533 (1980)
Name Status

Scientific Description

Family Convolvulaceae.

Habit and leaf form. Herbs, or herbaceous climbers; laticiferous, or non-laticiferous and without coloured juice. Autotrophic. Perennial; plants with neither basal nor terminal concentrations of leaves. Trailing or climbing; stem twiners, or scrambling. Helophytic, mesophytic, and xerophytic. Leaves alternate; spiral; petiolate; non-sheathing; simple. Leaf blades entire; pinnately veined, or palmately veined; cross-venulate; auriculate at the base, or hastate, or sagittate. Leaves without stipules. Leaf blade margins entire, or dentate. Leaves without a persistent basal meristem. Stem anatomy. Nodes unilacunar. Secondary thickening anomalous, or developing from a conventional cambial ring; via concentric cambia, or from a single cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’. Inflorescence few-flowered. Flowers in cymes. The terminal inflorescence unit cymose. Inflorescences axillary; with involucral bracts, or without involucral bracts. Flowers pedicellate; bracteate; bi- bracteolate; small to medium-sized; regular to somewhat irregular. The floral asymmetry (when noticeable) involving the perianth (K only). Flowers 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk present; annular. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx 5; 1 -whorled; polysepalous; glabrous; imbricate; regular to unequal but not bilabiate (subequal or the outermost slightly larger); persistent; accrescent; with the median member posterior. Corolla 5; 1 -whorled; gamopetalous; entire, or lobed. Corolla lobes markedly shorter than the tube. Corolla campanulate, or funnel-shaped; regular; glabrous abaxially; glabrous adaxially; white to cream (sometimes with a purple to brown centre). Androecium 5. Androecial members adnate (to the corolla); all equal to markedly unequal (actually slightly unequal); free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 5; remaining included; oppositisepalous. Anthers straight (when dehisced); dehiscing via longitudinal slits; introrse; tetrasporangiate. Pollen grains psilate. Gynoecium 2 carpelled, or 4 carpelled. The pistil 2 celled, or 4 celled. Gynoecium syncarpous; synstylovarious; superior. Ovary plurilocular; 2 locular, or 4 locular. Locules secondarily divided by ‘false septa’, or without ‘false septa’. Gynoecium median. Styles 1; simple (filiform); apical. Stigmas 2; 1 - lobed; globular; dry type; papillate (the papillae villiform); Group II type. Placentation basal. Ovules 1 per locule, or 2 per locule; ascending; apotropous; non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; not hairy; dehiscent; a capsule. Capsules loculicidal (via 4 valves). Seeds ovoid to trigonous; endospermic. Endosperm oily. Seeds not conspicuously hairy. Cotyledons 2. Embryo chlorophyllous; straight, or curved. 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, Northern Territory, and Queensland. Northern Botanical Province.

Additional characters Pollen grains foraminate (pantoporate). Stigmas the stigmatic area globose.

H.R. Coleman, 8 September 2016

Taxonomic Literature

  • Wheeler, J. R.; Rye, B. L.; Koch, B. L.; Wilson, A. J. G.; Western Australian Herbarium (1992). Flora of the Kimberley region. Western Australian Herbarium. Como, W.A.