Family Cabombaceae
Cabombaceae A. Rich.~ Nymphaeaceae Including Hydropeltideae (Hydropeltidaceae) Dum. 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, or alternate and opposite; 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. Fertile flowers hermaphrodite. Plants hermaphrodite. Pollination entomophilous. Inflorescence, floral, fruit and seed morphology. Flowers solitary; axillary; 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; isomerous. 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 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; 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; an aggregate. The fruiting carpel indehiscent; a follicle. Seeds endospermic. Perisperm present. Cotyledons 2. Physiology, biochemistry. Not cyanogenic. Alkaloids present. Saponins/sapogenins absent. Geography, cytology. Holarctic, Paleotropical, Neotropical, and Australian. Temperate to tropical. The monotypic Brasenia schreberi in tropical America, Africa, India and E. Australia, with Cabomba native to warm America but distributed worldwide via discarded aquarium plants. Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Nymphaeiflorae; Nymphaeales. Cronquist’s Subclass Magnoliidae; Nymphaeales. APG 3 peripheral angiosperms; Superorder Nymphaeanae; Order Nymphaeales. Species 8. Genera 2; Brasenia (B. schreberi), Cabomba (7 spp.). Economic uses, etc. Cabomba caroliniana is a declared noxious weed in nutrient rich shallow waters in North America and where introduced in Australia and Europe, clogging channels and drains and seriously restricting water flow and recreational activites. Illustrations. |
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