Habit and leaf form. Herbs. With a basal aggregation of leaves. Hydrophytic, or helophytic; when hydrophytic, rooted. Leaves alternate; spiral; petiolate; sheathing; simple, or compound; peltate (sometimes), or not peltate; when compound, ternate. Lamina when simple, entire; pinnately veined, or palmately veined; cross-venulate. Leaves exstipulate; without a persistent basal meristem.
Leaf anatomy. Hydathodes present. Stomata present; anomocytic.
The mesophyll with sclerencymatous idioblasts, or without sclerenchymatous idioblasts.
Stem anatomy. Nodes tri-lacunar, or penta-lacunar. Primary vascular tissue centrifugal. Cortical bundles present. Medullary bundles absent. Internal phloem absent. Secondary thickening absent, or developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem with vessels. Vessel end-walls simple, or scalariform and simple.
Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite; commonly heterostylous. Pollination entomophilous.
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in cymes, in heads, in fascicles, and in panicles. The ultimate inflorescence unit cymose, or racemose. Inflorescences scapiflorous, or not scapiflorous; fascicles, many flowered cymes, panicles or involucrate heads; with involucral bracts, or without involucral bracts. Flowers small to medium-sized; regular; usually 5 merous; cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk present; intrastaminal.
Perianth with distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous, or gamosepalous (sometimes connate); regular. Corolla 5; 1 whorled; appendiculate (with interstaminal scales), or not appendiculate; gamopetalous (with a tube); valvate (or induplicate-valvate); regular. Petals often fringed (or crested).
Androecium 5, or 10 (if the scales which sometimes alternate with the stamens are interpreted as staminodes). Androecial members adnate (to the tube); free of one another. Androecium exclusively of fertile stamens, or including staminodes (depending on interpretation of the scales). Staminodes if regarded as such, 5. Stamens 5; inserted near the base of the corolla tube, or midway down the corolla tube, or in the throat of the corolla tube; isomerous with the perianth; oppositisepalous (the filaments alternating with the C lobes). Anthers sagittate; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. Anther wall initially with one middle layer, or initially with more than one middle layer. Tapetum glandular. Pollen grains aperturate; 3 aperturate (usually), or 6 aperturate; colpate (sometimes parasyncolpate), or colporate, or rugate (exceptionally 6-rugate); 3-celled.
Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium syncarpous; synstylovarious; superior, or partly inferior. Ovary 1 locular. Gynoecium median; stylate. Styles 1 (shortly bifid); apical. Stigmas 2; wet type; papillate; Group III type. Placentation parietal (two placentas). Ovules in the single cavity 10–100 (‘many’); horizontal; anatropous; unitegmic; tenuinucellate. Endothelium differentiated. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed, or not formed (then the three nuclei degenerating early); when formed, 3; not proliferating; ephemeral to persistent. Synergids pear-shaped. Hypostase present, or absent. Endosperm formation cellular. Embryogeny asterad.
Fruit fleshy, or non-fleshy; dehiscent, or indehiscent; a capsule, or a berry. Capsules septicidal, or loculicidal, or valvular. Fruit 4–100 seeded (‘few to many’). Seeds endospermic. Endosperm oily. Seeds winged, or wingless. Cotyledons 2. Embryo straight.
Physiology, biochemistry. Not cyanogenic. Iridoids detected; ‘Route I’ type (normal and seco). Proanthocyanidins absent. Ellagic acid absent (Menyanthes). Saponins/sapogenins present, or absent. Inulin recorded.
Geography, cytology. Temperate. Cosmopolitan. X = 9, 17.
Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Gentianiflorae; Gentianales. Cronquist’s Subclass Asteridae; Solanales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; campanulid; Order Asterales.
Species 40. Genera 5; Liparophyllum, Menyanthes, Nephrophyllidium, Nymphoides, Villarsia.
• Menyanthes trifoliata (B. Ent.).
• Nymphoides peltata (B. Ent.).
• Nymphoides peltata (as Limnanthemum nymphoides): Eng. Bot. 921 (1866).