| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Aponogetonaceae J.G. Agardh

Habit and leaf form. Herbs; laticiferous. Perennial; cormous, or rhizomatous. Hydrophytic; rooted. Leaves emergent and floating. Often conspicuously heterophyllous. Leaves alternate; petiolate; sheathing. Leaf sheaths with free margins. Leaves simple. Lamina parallel-veined; cross-venulate (the tissue between the veins breaks up as the leaf matures, leaving a network with holes). Axillary scales present.

General anatomy. Plants with laticifers (articulated).

Leaf anatomy. Stomata present (on floating leaves); paracytic. Lamina without secretory cavities (assuming that Cronquist’s ‘with well developed secretory canals’ refer to laticifers). The mesophyll containing crystals. The crystals solitary-prismatic (? — no mention of raphides). Foliar vessels absent. Minor leaf veins without phloem transfer cells (Aponogeton).

Axial (stem, wood) anatomy. Secondary thickening absent. The axial xylem without vessels.

Root anatomy. Root xylem with vessels, or without vessels; vessel end-walls scalariform.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Floral nectaries present. Nectar secretion from the gynoecium (from the sides of the carpels). Pollination entomophilous; via beetles, or via hymenoptera.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (commonly projected above the water in 1–3 spikes). Inflorescences pseudanthial (sometimes), or not pseudanthial; spatheate (the spathe caducous). Flowers small; usually very irregular; when irregular (i.e. usually), zygomorphic. The floral irregularity involving the perianth. Flowers cyclic, or partially acyclic. Sometimes the gynoecium acyclic. Perigone tube absent.

Perianth of ‘tepals’, or absent; when present, (1–)2(–6); free; 1 whorled; petaloid; when present, white (usually), or blue, or purple.

Androecium 6 (usually 3 + 3), or 25–100 (i.e. sometimes ‘many’). Androecial members branched (when ‘many’), or unbranched; 2–4 whorled. Stamens 6(–50); diplostemonous to polystemonous. Anthers dehiscing via longitudinal slits; extrorse, or latrorse; tetrasporangiate. Endothecium developing fibrous thickenings. The endothecial thickenings spiral. Microsporogenesis successive, or simultaneous. The initial microspore tetrads tetrahedral, or decussate. Anther wall of the ‘monocot’ type. Pollen grains aperturate; 1 aperturate; sulcate; 3-celled.

Gynoecium (2–)3–6(–9) carpelled. Carpels isomerous with the perianth, or reduced in number relative to the perianth, or increased in number relative to the perianth. Gynoecium apocarpous; eu-apocarpous to semicarpous (basally fused to varying extents); superior. Carpel apically stigmatic; 1–8 ovuled. Placentation basal. The ‘odd’ carpel anterior. Stigmas dry type; papillate; Group II type. Ovules ascending; anatropous; crassinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; persistent. Synergids pear-shaped. Endosperm formation helobial.

Fruit non-fleshy; more or less an aggregate. The fruiting carpel dehiscent; a follicle. Seeds non-endospermic. Seeds with starch. Cotyledons 1 (bifacial). Embryo chlorophyllous; straight. Testa without phytomelan (?); fleshy or membranous.

Seedling. Germination phanerocotylar. Hypocotyl internode present (short). Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; dorsiventrally flattened. Coleoptile absent. Seedling non-macropodous. Seedling cataphylls absent. First leaf dorsiventral. Primary root ephemeral.

Physiology, phytochemistry. Accumulated starch exclusively ‘pteridophyte type’. Not cyanogenic. Alkaloids absent (2 species). Saponins/sapogenins absent. Proanthocyanidins present, or absent; when present, cyanidin. Flavonols present; kaempferol and quercetin, or quercetin. Ellagic acid absent.

Geography, cytology. Sub-tropical and tropical. Palaeotropical and South Africa. X = 8.

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

Species about 45. Genera 1; only genera, Aponogeton and Ouvirandra.

Economic uses, etc. Some aquarium and watergarden ornamentals.

Illustrations. • A. madagascariensis, as Ouvirandra: Bot. Mag. 82 (1856). • Le Maout and Decaisne: Aponogeton, Ouvirandra (= Aponogeton). • Aponogeton holubii: Hook Ic. Pl. 15 (1884). • Aponogeton natalense, Aponogeton rehmanni: Hook. Ic. Pl. 15 (1884). • Aponogeton distachyon: Hutchinson. • Aponogeton spathaceum var. junceum (cf. A. junceus): Bot. Mag. 104 (1878). • Ouvirandra bernieriana: Bot. Mag. 84 (1858).

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: 8th June 2026. delta-intkey.com’.

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