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The families of flowering plants

L. Watson and M.J. Dallwitz

Alismataceae Vent.

Including Damasoniaceae Nakai, Borboraceae Dulac (p.p.), Elismataceae Nak.; excluding Limnocharitaceae.

Habit and leaf form. Herbs; laticiferous. Annual (rarely), or perennial; with a basal aggregation of leaves; rhizomatous. Hydrophytic, or helophytic; rooted. Leaves submerged and emergent. Heterophyllous (often), or not heterophyllous. Leaves alternate; petiolate, or sessile; sheathing; simple. Lamina pinnately veined (or parallel-pinnate), or palmately veined, or parallel-veined; cross-venulate, or without cross-venules. Axillary scales present.

General anatomy. Plants without laticifers (the latex occuring in canals).

Leaf anatomy. Stomata present; paracytic, or tetracytic (rarely). Lamina with secretory cavities. Secretory cavities containing latex; schizogenous. The mesophyll containing crystals, or without crystals. The crystals druses (?), or solitary-prismatic (? — no raphides). Foliar vessels absent. Minor leaf veins without phloem transfer cells (4 genera).

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, or scalariform and simple (mostly mainly simple).

Reproductive type, pollination. Plants hermaphrodite, or monoecious, or dioecious (rarely), or polygamomonoecious. Floral nectaries present. Nectar secretion from the perianth, or from the gynoecium, or from the androecium (from the tepal or stamen bases in Echinodorus, but usually from the bases of the sides of the carpels).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (usually), or solitary. The ultimate inflorescence units cymose, or racemose. Inflorescences scapiflorous; paniculate, often complex with verticils of branches, sometimes umbellate through reduction of the whorls to one; with involucral bracts, or without involucral bracts. Flowers bracteate; regular; 3 merous; cyclic; tetracyclic to polycyclic. Perigone tube absent.

Perianth with distinct calyx and corolla; 6; free; 2 whorled; isomerous; different in the two whorls; white, or red, or pink (inner), or green (outer). Calyx 3; 1 whorled; polysepalous. Corolla 3; polypetalous; white, or red, or pink.

Androecium (3–)6 (in one cycle), or 18–100 (i.e. to many). Androecial members branched (usually, e.g. Alisma having three stamen pairs, while forms with numerous stamens have them seemingly spiralled, but actually reflecting whorls of trunk bundles), or unbranched (occasionally); when in more than one whorl, maturing centripetally; free of the perianth; free of one another (usually, ostensibly), or coherent (in pairs, or in anatomically determinable bundles); 1–20 whorled (i.e., to ‘many’ whorls). The androecial bundles (or the pairs, in Alisma) alternating with the corolla members. Androecium exclusively of fertile stamens. Stamens 3, or 6, or 18–100 (i.e. to ‘many’); reduced in number relative to the adjacent perianth, or isomerous with the perianth to polystemonous; alterniperianthial. Anthers dehiscing via longitudinal slits; extrorse. Endothecium developing fibrous thickenings. The endothecial thickenings girdling. Microsporogenesis successive. The initial microspore tetrads isobilateral. Anther wall of the ‘monocot’ type. Pollen grains aperturate; 2–3 aperturate, or 9–29 aperturate; foraminate; 3-celled.

Gynoecium 3 carpelled, or 6–100 carpelled (or more — i.e. to many); apocarpous; eu-apocarpous; superior. Carpel apically stigmatic, or with a lateral style, or with a gynobasic style; 1 ovuled, or 2 ovuled (rarely more). Placentation basal. Stigmas dry type; papillate; Group II type. Ovules ascending; anatropous, or amphitropous; weakly crassinucellate. Embryo-sac development Allium-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed, or not formed; when formed, 1; not proliferating. Synergids hooked (usually with filiform apparatus). Endosperm formation helobial, or nuclear (?).

Fruit non-fleshy; an aggregate. The fruiting carpels not coalescing. The fruiting carpel dehiscent, or indehiscent; a follicle, or an achene. Seeds non-endospermic. Seeds with starch. Cotyledons 1. Embryo achlorophyllous (3/5); strongly curved (horseshoe-shaped). Testa without phytomelan; usually membranous, sometimes thinly leathery, then brown.

Seedling. Germination phanerocotylar. Hypocotyl internode present (quite long, in Baldellia). Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; more or less circular in t.s. Coleoptile absent. Seedling macropodous. Seedling cataphylls absent. First leaf dorsiventral. Primary root ephemeral.

Physiology, phytochemistry. C3 and CAM. C3 physiology recorded directly in Alisma, Sagittaria. CAM recorded directly in Sagittaria subulata (aquatic CAM only). Anatomy non-C4 type (Sagittaria). Accumulated starch exclusively ‘pteridophyte type’. Cyanogenic (?), or not cyanogenic. Alkaloids present, or absent (2 species investigated). Iridoids not detected. Proanthocyanidins present, or absent; when present, cyanidin. Flavonols present, or absent; when present, kaempferol and quercetin. Ellagic acid absent. Sieve-tube plastids P-type; type II.

Geography, cytology. Temperate, sub-tropical, and tropical. Cosmopolitan. X = (5-)7–11(-13).

Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Alismatiflorae; Alismatales. APG III core angiosperms; Superorder Lilianae; non-commelinid Monocot. APG IV Order Alismatales.

Species 90. Genera 11; Alisma, Baldellia, Burnatia, Caldesia, Damasonium, Echinodorus, Limnophyton, Luronium, Ranalisma, Sagittaria, Wiesneria.

Economic uses, etc. Includes important aquarium and pond ornamentals, and some Sagittaria species have edible rhizomes.

Illustrations. • Le Maout and Decaisne: Alisma plantago-aquatica, Luronium natans. • Le Maout and Decaisne: Sagittaria, Damasonium. • Alisma plantago-aquatica (B. Ent., 1824). • Alisma plantago-aquatica: as A. plantago, Eng. Bot. 1437 (1869). • Baldellia ranunculoides: as Alisma, Eng. Bot. 1439 (1869). • Baldellia ranunculoides var. repens: as Alisma, Eng. Bot. 1440 (1869). • Caldesia parnassifolia, as Alisma reniformis: Wight’s Figs. of Indian Plants 2 (1843). • Damasonium alisma (B. Ent., 1839). • Limnophyton obtusifolium: Thonner. • Luronium natans: as Alisma, Eng. Bot. 1441 (1869). • Sagittaria montevidensis: Bot. Mag. 110 (1884). • Sagittaria sagittifolia (B. Ent., 1838). • Sagittaria sagittifolia: Eng. Bot. 1436 (1869).

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: 15th April 2018.’.