Wrightia R.Br.

Scientific Description

Family Apocynaceae.

Habit and leaf form. Perennial shrubs, or trees; evergreen, or deciduous; laticiferous (white). Plants unarmed. Leaves cauline. To 5–40 m high. Mesophytic. Not heterophyllous. Leaves medium-sized; opposite; ‘herbaceous’ to leathery; petiolate; simple. Leaf blades dorsiventral; entire; linear, or ovate, or obovate, or oblong, or elliptic; pinnately veined; cuneate at the base, or rounded at the base. Mature leaf blades adaxially glabrous, or pubescent (with simple basifixed trichomes); abaxially glabrous, or pubescent (with simple basifixed trichomes). Leaves without stipules. Leaf blade margins entire. Leaf anatomy. Hairs present; glandular hairs absent. Unicellular hairs present. Complex hairs absent. Branched hairs absent.

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

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’. Inflorescence few-flowered to many-flowered. Flowers in cymes. Inflorescences terminal; dichasial or monochasial inflorescence. Flowers pedicellate; bracteate; small; fragrant; regular; 5 merous; tetracyclic. Hypogynous disk absent. Perianth with distinct calyx and corolla; 10; 2 -whorled; isomerous. Calyx present; 5; 1 -whorled; gamosepalous; lobed (lobes are deeply divided); lobulate. Calyx lobes markedly longer than the tube. Calyx erect; hairy; exceeded by the corolla; regular. Calyx lobes elliptic, or obovate. Corolla present; 5; 1 -whorled; appendiculate (corolline corona of 5-many subentire, dentate, laciniate or fimbriate segments, distinct or coherent to form a tube); gamopetalous; lobed; lobulate. Corolla lobes markedly longer than the tube. Corolla contorted (sinistrorse in bud); sub- rotate, or campanulate, or funnel-shaped, or hypocrateriform; regular; glabrous abaxially; glabrous adaxially (commonly), or hairy adaxially (rarely); plain; white, or yellow, or orange. Corolla lobes ovate, or obovate. Androecial members definite in number. Androecium 5. Androecial members adnate (epipetalous); all equal; free of one another; 1 -whorled. Stamens 5. Staminal insertion in the throat of the corolla tube. Stamens all inserted at the same level; becoming exserted; all more or less similar in shape; isomerous with the perianth; oppositisepalous; all alternating with the corolla members. Anthers all alike; dehiscing via longitudinal slits; appendaged. The anther appendages apical. Anthers apiculate. Gynoecium 2 carpelled. The pistil 2 celled. Gynoecium syncarpous (the carpels united only by their styles); eu-syncarpous; superior. Ovary plurilocular; 2 locular. Gynoecium stylate. Styles 1. Stigmas 1. Placentation axile.

Fruit and seed features. Fruit 110–300 mm long; non-fleshy; a schizocarp. Mericarps comprising follicles (2; dehiscing ventrally). Dispersal unit the seed. Fruit 30–50 seeded (i.e. ‘many’). Seeds not compressed (linear-fusiform to linear-oblong); medium sized; conspicuously hairy; with a tuft of hairs (white hairs at chalazal end); wingless.

Geography, cytology, number of species. World distribution: Africa, Asia, Malesia and Australia. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia, Northern Territory, and Queensland. Northern Botanical Province. A genus of c. 16 species; 2 species in Western Australia; 0 endemic to Western Australia.

Additional comments. Etymology: named for William Wright, a medical practitioner and ardent amateur botanist.

Etymology. After William Wright (1735–1819), Scottish physician and botanist; travelled in Greenland, Jamaica and Barbados; his herbarium is now at the British Museum and Liverpool University.