Teucrium L.

Scientific Description

Common name. Germanders. Family Lamiaceae.

Habit and leaf form. Herbs, or shrubs; evergreen; bearing essential oils. Plants unarmed. Perennial. Leaves cauline. Plants with neither basal nor terminal concentrations of leaves. Young stems usually tetragonal. To 0.05–0.6 m high. Leaves small to medium-sized; not fasciculate; opposite; not decurrent on the stems; not imbricate; more or less sessile; foetid; simple; epulvinate. Leaf blades dissected, or entire; flat; narrow ovate; irregularly pinnatifid, or much-divided; one-veined, or pinnately veined, or pinnately veined to palmately veined; cross-venulate; cuneate at the base. Mature leaf blades adaxially more or less densely pilose; abaxially pilose. Leaves without stipules. Leaf blade margins entire, or serrate; flat, or involute. 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’. The terminal inflorescence unit cymose. Inflorescences sometimes branched or unbranched inflorescences in ES species. Flowers pedicellate; small; somewhat 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; more or less regularly blunt-lobed, or toothed; imbricate, or open in bud; exceeded by the corolla to exceeding the corolla; campanulate, or tubular; regular; non-fleshy; persistent; with the median member posterior. Calyx lobes ovate. Corolla present; disguisedly 5; 1 -whorled; gamopetalous; blunt-lobed; imbricate; unequal but not bilabiate to bilabiate (ostensibly 1-lipped, this 5 lobed, with the upper lip component much reduced and deeply cleft); plain; white, or cream. Corolla lobes broadly oblong, or oblong. Corolla members entire. Androecium present. Fertile stamens present. Androecial members definite in number. Androecium 4. Androecial members adnate; markedly unequal; free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 4. Staminal insertion near the base of the corolla tube, or midway down the corolla tube. Stamens 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 filiform. Anthers connivent, or separate from one another; dorsifixed; versatile, or non-versatile; dehiscing via longitudinal slits; introrse; bilocular (loculi strongly divergent); 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; apical; 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 aggregated in dense heads, or aggregated in dense spicate inflorescences, or separated by extended internodes. 2(–15) flowers subtended by each floral leaf. Calyx limb 5 lobed. Corolla tube usually not exceeding the calyx. The upper lip of the corolla incorporating 2 members, the lower 3, or suppressed, the lower incorporating all five members; (posterior, adaxial) lip of the corolla bilobed. Lower (abaxial) lip of the corolla three lobed, or five lobed if the upper lip is not detected as such; not concave. Stamens ascending (strongly exserted between the lobes of the vestigial ‘upper lip’).

Geography, cytology, number of species. Native of Australia. Endemic to Australia. Australian states and territories: Western Australia, South Australia, Queensland, New South Wales, Victoria, and Tasmania. A genus of ca 300 species; 7 species in Western Australia; 7 endemic to Western Australia.

Etymology. From the Greek teucrion; name used by Dioscorides for more than one species of the genus; said to refer to Teucer, king of Troy, who first used the plant in medicine.