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Blyxa Thouars

Gen.Nov.Madagasc. 4 (1806)
Name Status

Scientific Description

Family Hydrocharitaceae.

Habit and leaf form. Aquatic herbs. Annual, or perennial. Leaves basal (usually), or cauline. Plants with a basal concentration of leaves, or with neither basal nor terminal concentrations of leaves; often stoloniferous. Hydrophytic; non-marine; rooted. Leaves submerged. Not heterophyllous. Leaves alternate; spiral; membranous, or ‘herbaceous’; sessile; sheathing. Leaf sheaths with free margins. Leaves simple; epulvinate. Leaf blades entire; linear; 1–11 -nerved; one-veined, or parallel-veined; without cross-venules (cross-veins faint or absent). Leaves without stipules. Axillary scales present (usually 2, white, triangular, entire). Leaf blade margins minutely serrulate. Leaves with a persistent basal meristem, and basipetal development. Leaf anatomy. Hairs absent. Stem anatomy. Secondary thickening absent.

Reproductive type, pollination. Fertile flowers hermaphrodite, or functionally male, or functionally female. Unisexual flowers present, or absent. Plants hermaphrodite, or dioecious, or monoecious (perhaps). Female flowers and bisexual flowers solitary (or rarely 2, reaching water surface by elongation of perigone tube or sometimes remaining emerged and cleistogamous). Male flowers aggregated in ‘inflorescences’ (3–20 per spathe, reaching water surface by elongation of pedicel). Floral nectaries absent. Entomophilous, or pollinated by water.

Inflorescence and flower features. Flowers solitary, or aggregated in ‘inflorescences’; in cymes. The terminal inflorescence unit (when flowers clustered) cymose. Inflorescences scapiflorous, or not scapiflorous; axillary; spatheate (spathe bracts 2, connate except at apex, with 3 longitudinal ribs). Flowers pedicellate (male flowers), or sessile (female flowers); small; regular; 3 merous; partially acyclic. The gynoecium acyclic. Perigone tube present. Perianth with distinct calyx and corolla; 6; 2 -whorled; isomerous. Calyx 3; 1 -whorled; polysepalous (but remaining tubular during anthesis); regular; green; persistent. Sepals ovate to linear. Corolla 3; 1 -whorled; polypetalous; papillose; white, or red. Petals petaloid or capillary; clawed, or sessile. Fertile stamens present, or absent (female flowers). Androecium 6, or 9 (usually), or 3 (in bisexual species). Androecial members free of the perianth; free of one another; 1–3 -whorled (the whorls trimerous). Androecium exclusively of fertile stamens. Stamens 3, or 6, or 9; isomerous with the perianth to triplostemonous; alterniperianthial, or oppositiperianthial. Anthers dehiscing via short slits; latrorse, or introrse; four locular; bisporangiate, or tetrasporangiate. Pollen shed as single grains. Fertile gynoecium present, or absent (male flowers). Gynoecium 3 carpelled. The pistil 1 celled (with 3 placentae). Gynoecium syncarpous; synovarious to synstylovarious; inferior. Ovary unilocular; 1 locular (but with deeply intruding partial partitions). Styles 3; simple; apical. Stigmas 3; 1 - lobed; dry type; papillate; Group II type. Placentation laminar-dispersed. Ovules in the single cavity 12–100 (i.e. ‘many’); pendulous to ascending; non-arillate; anatropous.

Fruit and seed features. Fruit fleshy, or non-fleshy; indehiscent (opening by decay); capsular-indehiscent. Dispersal by water. Fruit numerous-seeded. Seeds ellipsoidal or fusiform; scantily endospermic, or non-endospermic; winged, or wingless; with starch. Cotyledons 1. Embryo straight. Seedling. Hypocotyl internode present. Mesocotyl absent. Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; dorsiventrally flattened. Coleoptile absent. Seedling macropodous. Seedling cataphylls absent. First leaf dorsiventral. Primary root ephemeral.

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 Stigmas the stigmatic area linear.

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..