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Plectranthus L'Her.

This name is not current. Find out more information on related names.

Stirp.Nov. 84 (1788)
Name Status
Not Current

Scientific Description

Common name. Plectranthus. Family Lamiaceae.

Habit and leaf form. Herbs, or shrubs; evergreen; bearing essential oils. Plants unarmed. Annual, or perennial. Leaves cauline. Plants with neither basal nor terminal concentrations of leaves. Young stems usually tetragonal. To 0.3–1.5 m high. Leptocaul. Leaves small to medium-sized; not fasciculate; opposite; membranous (blade); not imbricate; petiolate; aromatic; simple; epulvinate. Leaf blades entire; flat; ovate, or elliptic; one-veined; cross-venulate; cuneate at the base (to subtruncate). Mature leaf blades adaxially woolly; abaxially woolly. Leaves without stipules. Leaf blade margins undulate- crenate; flat. Leaves without a persistent basal meristem. Leaf anatomy. Hairs present; glandular hairs present; complex hairs absent. Branched hairs present. Urticating hairs absent. Stem anatomy. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Entomophilous, or ornithophilous; usually via hymenoptera, or via lepidoptera, or via diptera.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’. Inflorescence many-flowered. Flowers in verticils. The terminal inflorescence unit cymose. Inflorescences terminal; unbranched or branched; units cymose, arranged in pseudo-whorls. Flowers sessile, or subsessile; bracteate; minute to small; very irregular; zygomorphic; cyclic; tetracyclic. Floral receptacle developing a gynophore, or with neither androphore nor gynophore. Free hypanthium absent. Perianth with distinct calyx and corolla; 4–10; 2 -whorled; isomerous, or anisomerous. Calyx present; 5; 1 -whorled; gamosepalous; blunt-lobed, or toothed; imbricate, or open in bud; exceeded by the corolla; tubular, or campanulate; unequal but not bilabiate, or bilabiate (subequally 5-toothed or with abaxial lobe divided into 2 triangular teeth and the 2 triangular lateral lobes similar but with adaxial lobe usually broadly ovate); non-fleshy; persistent; accrescent; with the median member posterior. Calyx lobes broadly ovate, or triangular. Corolla present; disguisedly 5; 1 -whorled; gamopetalous; blunt-lobed; imbricate; bilabiate (the upper lip short, 4 lobed and recurved, the lower lip larger, entire or notched, long boat-shaped); with contrasting markings; white, or blue to violet. Corolla lobes more or less obovate. Corolla members entire. Fertile stamens present. Androecial members definite in number. Androecium 4. Androecial members adnate; markedly unequal; free of one another (connate at base for ca 1 mm); 1 -whorled. Androecium exclusively of fertile stamens. Stamens 4. Staminal insertion in the throat of the corolla tube. Stamens inserted at markedly different levels; becoming exserted; didynamous; all more or less similar in shape; reduced in number relative to the adjacent perianth; fertile stamens representing the posterior-lateral pair and the anterior-lateral pair; oppositisepalous; all alternating with the corolla members. Filaments glabrous; filiform. Anthers connivent, or separate from one another; dorsifixed; versatile, or non-versatile; dehiscing via longitudinal slits; introrse; unilocular to bilocular; tetrasporangiate; unappendaged. Pollen shed as single grains. Fertile gynoecium present. Gynoecium 2 carpelled (the carpels deeply lobed to mimic G4). The pistil 4 celled. Carpels reduced in number relative to the perianth. Gynoecium syncarpous; synstylovarious to eu-syncarpous; superior. Ovary plurilocular; 2 locular (originally), or 4 locular (by intrusions of the ovary wall constituting ‘false septa’). Locules secondarily divided by ‘false septa’. Gynoecium median; stylate. Styles 1; simple; from a depression at the top of the ovary (the ovary deeply lobed); ‘gynobasic’; becoming exserted. Stigmas 2, or 1 (by reduction); 2 - lobed. Placentation basal. Ovules 2 per locule, or 1 per locule (two per original loculus, but one per locellus); ascending; apotropous; non-arillate; anatropous, or hemianatropous.

Fruit and seed features. Fruit non-fleshy, or fleshy; a schizocarp. Mericarps (2–)4; comprising nutlets. Seeds endospermic to non-endospermic. Embryo well differentiated. Cotyledons 2. Embryo straight.

Special features. The flowering nodes separated by extended internodes. 3–15 flowers subtended by each floral leaf. Calyx limb 5 lobed. Corolla tube exceeding the calyx; basally bent. The upper lip of the corolla incorporating 4 members, the lower 1; (posterior, adaxial) lip of the corolla 3 lobed (representing the adaxial and lateral members, the median sometimes itself bilobed); upper (adaxial) lip of the corolla not concave. Lower (abaxial) lip of the corolla entire to bilobed (entire to notched); markedly concave. Stamens projecting straight forwards or spreading, or descending.

Geography, cytology, number of species. Native of Australia. Not endemic to Australia. Australian states and territories: Western Australia and Queensland (?NT). Northern Botanical Province. A genus of ca 300 species; 2 species in Western Australia; 0 endemic to Western Australia.

Etymology. From the Greek for "cock's spur" and "flower"; refers to the spurred or gibbous base of the corolla.

T.R. Lally, 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..