Habit and leaf form. Aquatic herbs; laticiferous, or non-laticiferous and without coloured juice. Perennial; rhizomatous. Hydrophytic; rooted. Leaves submerged, or submerged and floating. Not heterophyllous (Brasenia), or heterophyllous (Cabomba). Leaves alternate; spiral, or distichous, or four-ranked; non-sheathing; not gland-dotted; simple, or simple and compound; peltate (in Brasenia), or not peltate; epulvinate. Lamina dissected (submerged leaves), or entire (floating leaves); when dissected, finely dichotomously dissected; often cordate. Leaves exstipulate.
Leaf anatomy. The mesophyll containing mucilage cells, or not containing mucilage cells; without sclerenchymatous idioblasts. Minor leaf veins without phloem transfer cells (Cabomba).
Stem anatomy. Secretory cavities present (articulated); with latex. Cork cambium absent. Primary vascular tissue in scattered bundles. Secondary thickening absent. Xylem presumably with tracheids; without vessels. Sieve-tube plastids S-type.
Reproductive type, pollination. Hermaphrodite. Entomophilous.
Inflorescence, floral, fruit and seed morphology. Flowers solitary; 3 merous; cyclic, or partially acyclic. When acyclic the gynoecium acyclic, or the androecium acyclic and the gynoecium acyclic. Free hypanthium absent.
Perianth with distinct calyx and corolla (but the calyx petaloid); 6; 2 whorled; anisomerous. Calyx 3 (petaloid); 1 whorled; polysepalous; regular. Corolla 3; 1 whorled; polypetalous; regular; yellow, or purple, or white. Petals clawed, or sessile.
Androecium 3-6 (Cabomba), or 12-18 (Brasenia). Androecial members when many, maturing centripetally; free of the perianth; all equal; free of one another. Androecium exclusively of fertile stamens. Stamens 3-6, or 12-18; isomerous with the perianth to diplostemonous, or polystemonous; filantherous (with the filaments somewhat flattened). Anthers dehiscing via longitudinal slits; extrorse; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 1 - aperturate; sulcate (sometimes trichotomosulcate).
Gynoecium (2-)3-18. 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; superior. Carpel non-stylate, or stylate (stigma then subsessile); with a longitudinal stigmatic surface (Brasenia), or apically stigmatic (Cabomba); (1-)2 ovuled, or 3 ovuled. Placentation marginal. Ovules pendulous; non-arillate; anatropous; bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Endosperm formation helobial. Endosperm haustoria present; chalazal.
Fruit non-fleshy; multiple. The fruiting carpel indehiscent; a follicle. Seeds endospermic. Perisperm present. Cotyledons 2.
Physiology, biochemistry. Not cyanogenic. Alkaloids present. Saponins/sapogenins absent.
Geography, cytology. Temperate to tropical. Cosmopolitan, except Europe.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren's Superorder Nymphaeiflorae; Nymphaeales. Cronquist's Subclass Magnoliidae; Nymphaeales. Takhtajan's Subclass Magnoliidae; Nymphaeanae; Nymphaeales. Species 7. Genera 2; Brasenia, Cabomba.
Illustrations. cabom209.gif
Additional, to be intercalated. Flowers axillary.
