Lythrum L.
Sp.Pl. 2:446 (1753)

Name Status: Current
Browse to the list of specimens for Lythrum L.

Scientific Description
H.R. Coleman, Thursday 8 September 2016

Common name. Loosestrifes. Family Lythraceae.

Habit and leaf form. Sub- shrubs, or herbs. Herbs annual, or perennial. Young stems cylindrical, or tetragonal. Helophytic to xerophytic. Leaves alternate, or opposite, or whorled; when alternate, spiral; 3 per whorl; petiolate to subsessile, or sessile; gland-dotted, or not gland-dotted; simple. Leaf blades entire; elliptic, or oblong, or ovate, or linear; pinnately veined; cross-venulate; auriculate at the base, or attenuate at the base, or rounded at the base (or stem-clasping or obtuse). Leaves without stipules. Leaf blade margins entire. Leaves without a persistent basal meristem. Stem anatomy. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Plants homostylous (di- or trimorphic). Entomophilous.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; in cymes, or in fascicles (or clusters). The terminal inflorescence unit cymose, or racemose. Inflorescences axillary. Flowers pedicellate, or sessile; bracteolate; minute to medium-sized; regular; 4 merous, or 6 merous; pentacyclic. Floral receptacle developing an androphore, or with neither androphore nor gynophore. Free hypanthium present; narrowly campanulate, or tubular; ribbed; sinus appendages present, elongate. Hypogynous disk present, or absent. Perianth with distinct calyx and corolla; (3–)8–16(–32); 2 -whorled; isomerous. Calyx present; 4–6; 1 -whorled; gamosepalous; blunt-lobed; lobes valvate; tubular, or campanulate, or urceolate; unequal but not bilabiate, or regular; persistent. Calyx lobes triangular (to deltate). Epicalyx present, or absent. Corolla present, or absent (rarely); 4–6; 1 -whorled; polypetalous; plicate; unequal but not bilabiate, or regular; pink, or purple, or blue. Petals ovate, or obovate; sessile. Androecial members definite in number. Androecium 2–12. Androecial sequence determinable, or not determinable. Androecial members when determinable, maturing centripetally; adnate (to the hypanthium, low down); markedly unequal (dimorphic); free of one another; 1–3 -whorled (or several). Androecium exclusively of fertile stamens. Stamens 2–12; attached inside the hypanthium; all more or less similar in shape; reduced in number relative to the adjacent perianth to isomerous with the perianth to polystemonous; oppositisepalous; inflexed in bud, or erect in bud. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Gynoecium 2 carpelled. The pistil 2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary plurilocular; 2 locular; sessile to stipitate. Gynoecium stylate. Styles 1; apical. Stigmas 1; capitate. Placentation axile. Ovules (1–)5–50 per locule; ascending, or horizontal; non-arillate; anatropous.

Fruit and seed features. Fruit non-fleshy; dehiscent; a capsule. Capsules septicidal. Seeds non-endospermic; wingless. Cotyledons 2. Embryo straight.

Etymology. From the Greek for "black blood"; generally thought to refer to the purple colour of the flowers of some species, but it has been suggested that it refers to some styptic property of the plant.

Taxonomic Literature

  • Wheeler, Judy; Marchant, Neville; Lewington, Margaret; Graham, Lorraine (2002). Flora of the south west, Bunbury, Augusta, Denmark. Volume 2, dicotyledons. Australian Biological Resources Study. Canberra.
  • Lepschi, B. J. (2000). A review of the genus Lythrum (Lythraceae) in Western Australia, including typification of L. paradoxum.
  • Grieve, B. J.; Blackall, W. E. (1998). How to know Western Australian wildflowers : a key to the flora of the extratropical regions of Western Australia. Part II, Dicotyledons (Amaranthaceae to Lythraceae). University of W.A. Press. Nedlands, W.A.
  • Marchant, N. G.; Wheeler, J. R.; Rye, B. L.; Bennett, E. M.; Lander, N. S.; Macfarlane, T. D.; Western Australian Herbarium (1987). Flora of the Perth region. Part one. Western Australian Herbarium. Perth.