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~ Alismataceae.
Habit and leaf form. Aquatic herbs; laticiferous. Without conspicuous aggregations of leaves. Hydrophytic; free floating, or rooted. Leaves of rooted plants submerged and emergent. Conspicuously heterophyllous (the submerged leaves linear, the emergent leaves petiolate with lanceolate or ovate lamina), or not conspicuously heterophyllous. Leaves alternate; spiral to distichous (spirodistichous); at least when emergent, petiolate; sheathing. Leaf sheaths with free margins. Leaves simple; epulvinate. Lamina entire; linear, or lanceolate, or oblong, or obovate; parallel-veined, or pinnately veined (parallel-pinnate in the mature blade); cross-venulate. Axillary scales present. Lamina margins entire.
General anatomy. Plants without laticifers.
Leaf anatomy. Stomata present; paracytic. Lamina with secretory cavities. Secretory cavities containing latex. The mesophyll not containing mucilage cells; without crystals. Foliar vessels absent. Minor leaf veins without phloem transfer cells (Hydrocleys, Limnocharis).
Axial (stem, wood) anatomy. Secretory cavities present; with latex. Secondary thickening absent. The axial xylem without vessels.
Root anatomy. Root xylem with vessels; vessel end-walls scalariform and simple.
Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present. Nectar secretion from the gynoecium (basally from the bases of the sides of the carpels).
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in umbels (‘pseudo-umbels’). The ultimate inflorescence units cymose. Inflorescences scapiflorous; terminal; panicle-derived pseudo-umbels; with involucral bracts. Flowers bracteate; regular; 3 merous; cyclic, or partially acyclic. Sometimes the androecium acyclic. Perigone tube absent.
Perianth with distinct calyx and corolla; 6; free; 2 whorled; isomerous; different in the two whorls; white, or red (inner), or green (outer). Calyx 3; 1 whorled; polysepalous; regular; persistent. Corolla 3; 1 whorled; polypetalous; regular; white, or yellow; deciduous.
Androecium 3, or 6, or 7–100 (i.e. to ‘many’). Androecial members branched, or unbranched; when with trunk bundles, maturing centrifugally; free of the perianth; free of one another, or coherent (then with ‘trunk bundles’). Androecium exclusively of fertile stamens, or including staminodes (the outer members often staminodial). Staminodes external to the fertile stamens. Stamens 3, or 6, or 7–100 (to ‘many’); isomerous with the perianth to polystemonous. Anthers dehiscing via longitudinal slits; extrorse, or latrorse; tetrasporangiate. Endothecium developing fibrous thickenings. The endothecial thickenings girdling. Anther epidermis persistent. Microsporogenesis successive. Anther wall initially with one middle layer; of the ‘monocot’ type. Tapetum amoeboid. Pollen grains aperturate, or nonaperturate; when aperturate, (3–)4–9 aperturate; tri- to poly- foraminate; 3-celled (in all three genera).
Gynoecium 3 carpelled, or 5–9 carpelled, or 12–20 carpelled (all in one whorl). Carpels isomerous with the perianth. Gynoecium apocarpous; eu-apocarpous, or semicarpous (sometimes basally weakly connate); superior. Carpel distally incompletely closed, or fully closed; 12–100 ovuled (‘many’). Placentation dispersed. Ovules over the carpel surface; anatropous to campylotropous; bitegmic; pseudocrassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Allium-type. Endosperm formation helobial. Embryogeny caryophyllad.
Fruit non-fleshy; an aggregate (in a head). The fruiting carpel dehiscent; a follicle. Seeds non-endospermic. Cotyledons 1. Embryo curved (horseshoe shaped), or bent. Testa without phytomelan.
Seedling. Germination phanerocotylar. Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; more or less circular in t.s. Coleoptile absent. Seedling macropodous. First leaf dorsiventral. Primary root ephemeral.
Physiology, phytochemistry. Alkaloids absent. Saponins/sapogenins absent. Proanthocyanidins absent. Sieve-tube plastids P-type; type II.
Geography, cytology. Tropical. Widespread tropical. X = 7, 8, 10 (the chromosomes large).
Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Alismatiflorae; Hydrocharitales. APG III core angiosperms; Superorder Lilianae; non-commelinid Monocot. APG IV Order Alismatales (as a synonym of Alismataceae?).
Species 12. Genera 3; Butomopsis, Hydrocleys, Limnocharis.
General remarks. Supposedly differing from Alismataceae sensu stricto (q.v.) in the centrifugally maturing androecium, as well as the gynoecium with numerous, dispersed, pseudocrassinucellate ovules.
Illustrations. • Hydrocleys nymphoides: Hutchinson. • Hydrocleys nymphoides (as Limnocharis): Bot. Mag. 60 (1833). • Limnocharis plumieri: Bot. Mag. 52 (1825). • Le Maout and Decaisne: Hydrocleys, Limnocharis.
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 4th May 2024. delta-intkey.com’.
