NYMPHAEALES Dumort

Hydropeltidopsida Bartl., Ord. Nat. Plant.: 78, 86. Sep 1830 [’Hydropeltideae’]; Hydropeltidales Spenn., Handb. Angew. Bot. 1: 202. 1-19 Jul 1834 [‘Hydropeltideae’]; Nymphaeopsida Horan., Prim. Lin. Syst. Nat.: 55. 2 Nov 1834 [’Nymphaeales’]; Cabombales Rich. in C. F. P. von Martius, Consp. Regn. Veg.: 38. Sep-Oct 1835 [‘Cabombeae’]; Euryalales H. L. Li in Amer. Midl. Naturalist 54: 39. 27 Aug 1955; Nymphaeanae Thorne ex Reveal in Novon 2: 236. 13 Oct 1992; Barclayales Doweld, Tent. Syst. Plant. Vasc.: xxiii. 23 Dec 2001

Fossil Pluricarpellatia peltata is the oldest known fossil of presumably nymphaealean origin and was described from the Late Aptian to Early Albian (the Early Cretaceous, 125–115Mya) layers of Brazil. This probably aquatic species had peltate leaves and an apocarpous gynoecium. A number of fossil seeds, leaves and pollen are known from the Late Cretaceous of, e.g., Europe, North America, Israel, and Japan. There is also a vast fossil record of Nymphaeales from the Cenozoic of Portugal and eastern North America, consisting of leaves, roots, stems and reproductive organs including seeds. These can be assigned to extant groups as well as to the fossil Braseniella, Dusembaya, Eoeuryale, Irtyshenia, Nikitinella, Palaeoeuryale, Palaeonymphaea, Protobarclaya, Pseudoeuryale, Sabrenia, Tavdenia and Tomskiella.

Habit Usually bisexual (rarely monoecious or dioecious), usually perennial (rarely annual) herbs. Aquatic. Usually with a rhizome or tuberous stem (some species stoloniferous).

Vegetative anatomy Mycorrhiza absent. Primary root ephemeral, replaced by adventitious roots, initiated from the nodes (single root arising from point below each leaf); proximal cell comparatively small; root cap enlarged; root cap and epidermis not of common ontogenetical origin; secondary dermatogen present in root apex; root epidermis with short cells alternating with long cells; root endodermis with casparian strips; root aerenchyma interrupted by diaphragms. Phellogen absent. Epidermis initiated from outer cortical layer. Primary stem with scattered closed vascular bundles; axial vascular bundles concentric. Stem vascular tissue complex near nodes. Development of primary xylem mesarch; primary xylem with tracheids (with annular, spiral or reticulate secondary cell wall thickenings) and protoxylem with lacunae. Cambium and secondary lateral growth absent. Vessels or vessel-like elements (primary protoxylem lacunae, present in root primary xylem) with complex to scalariform perforation plates; lateral pits scalariform, simple pits. Imperforate tracheary xylem elements tracheids with annular or spiral secondary cell wall thickenings and with simple pits. Wood rays absent. Axial parenchyma? Sieve tube plastids usually S type (sometimes P2c type). Nodes 3:3, trilacunar with three leaf traces, or 1:2, unilacunar with two traces, or more complex. Trichoblasts in vertical rows and articulated unbranched laticifers usually abundant. Sclerenchymatous idioblasts and sclereids present or absent; sclereids when present stellate to girdle- or H-shaped; asterosclereids with calciumoxalate crystals often frequent in cell walls. Starch grains complex. Tanniniferous parenchyma cells often abundant in rhizome. Silica probably absent.

Trichomes Hairs tricellular or quadricellular, uniseriate, simple, often as secretory mucilage hairs or nectariferous hairs with large terminal cell, hydropotes.

Leaves Alternate (spiral), simple, entire, peltate, or much divided (sometimes linear to filiform), usually with involute ptyxis, usually floating or submersed. Stipules adaxial and bicarinate, pairwise and lateral, or absent; leaf sheath absent. Petiole vascular bundle? Venation palmate, actinodromous, brochidodromous or semidichotomous. Stomata stephanocytic or anomocytic, only on adaxial side of leaf, or absent. Cuticular waxes absent. Mesophyll with sclerenchymatous idioblasts (asterosclereids present), with or without mucilage cells. Idioblasts with ethereal oils absent. Leaf margin serrate, sinuate or entire.

Inflorescence Flowers solitary, axillary or extra-axillary, often not in normal axillary position, alternating with leaves in foliar spiral or arising from separate spirals (sometimes terminal, capitate, bisexual pseudanthia surrounded by membranous bracts, with central male flowers surrounded by female flowers). Bracts usually absent.

Flowers Actinomorphic. Hypanthium usually present. Hypogyny to epigyny. Tepals spiral or whorled, with imbricate aestivation, usually free (sometimes absent), at least inner ones probably extrastaminal staminodia; outer (two to) four to six (to twelve) tepals sepaloid to petaloid; inner two to more than 70 tepals (sometimes absent) usually petaloid staminodia with nectaries (nectaries rarely spur-like or absent). Disc absent.

Androecium Stamens 14 to more than 200, spiral or whorled, usually broad, three-veined, free, outwards and inwards often grading into staminodia (stamens rarely with narrow filaments). Anthers basifixed, non-versatile, tetrasporangiate, usually introrse (sometimes latrorse, rarely extrorse), longicidal (dehiscing usually with longitudinal slits, sometimes H-shaped). Tapetum usually secretory or amoeboid-periplasmodial. Staminodia often numerous.

Pollen grains Microsporogenesis usually simultaneous (rarely successive). Pollen grains globose or boat-shaped, usually zonasulculate (with band-shaped aperture encircling equator; sometimes anasulcate; rarely inaperturate? or anatrichotomocolpate), usually shed as monads (in ’Victoria clade’ of Nymphaea as tetrads), bicellular or tricellular at dispersal. Exine tectate, with granular, intermediary or columellate infratectum, perforate, microperforate, scabrate or striate, spinulate, verrucate, echinulate or psilate.

Gynoecium Pistil composed of (one or) three to c. 35 conduplicate carpels, whorled, free or partially or entirely connate; carpel usually ascidiate (rarely plicate or intermediary), postgenitally occluded by secretion, with secretory canal; extragynoecial compitum probably absent; carpels usually with uniseriate hairs with tanniniferous elongate terminal cell. Ovary superior to inferior, usually multilocular (sometimes unilocular). Style transformed into carpellary appendages, or single, or absent. Stigmas usually capitate, with receptive surfaces radiating from centre (rarely deeply decurrent, sometimes penicillate consisting of hairs), papillate (with multicellular papillae) or non-papillate, usually Wet (sometimes Dry) type. Pistillodium absent.

Ovules Placentation usually laminar (sometimes apical). Ovules (one to) numerous per carpel, usually anatropous, pendulous (rarely orthotropous, horizontal), bitegmic, crassinucellar. Micropyle endostomal to bistomal. Nucellar cap sometimes present. Megagametophyte monosporous, quadrinucleate and quadricellular, Nuphar/Schisandra type. Antipodal cells absent. A single uninucleate haploid central cell. The two nuclei after first division present at micropylar pool. Egg cell differentiated from one of the three micropylar cells after second division. One sperm nucleus and one polar nucleus fusing during second fertilization. Endosperm development usually cellular (rarely helobial or nuclear). Endosperm cells diploid. Endosperm haustorium chalazal. Embryogenesis asterad.

Fruit Usually a berry-like capsule with fleshy spongy tissue, dehiscing dorsally to irregularly (sometimes an achene-like follicle; rarely an assemblage of achenes).

Seeds Funicular aril usually present. Operculum dehiscent at germination, present at micropylar end. Seed coat exotestal. Exotesta often palisade. Mesotesta and endotesta unspecialized. Tegmen usually unspecialized. Perisperm well developed, usually copious, starchy, containing multinucleate cells with compound starch grains, or absent. Endosperm scarse, little developed, enclosing embryo at micropylar end. Embryo small, slightly triangular to broad, with or without chlorophyll. Suspensor absent. Cotyledons (one or) two, more or less fused. Germination phanerocotylar or cryptocotylar. Radicula ephemeral. Seedlings and young plants monopodial, with linear first leaves.

DNA An intergenic inversion of c. 200 bp is present in the plastid inverted repeat (IR region). Exon 5’ in PI-homologues 42 bp, at least in Nymphaeaceae (ancestral character state among angiosperms).

Phytochemistry Flavonols (kaempferol, quercetin, myricetin), flavone-C-glycosides, ellagic and gallic acid, hydrolyzable gallo- and ellagitannins (ellagitannins different from those occurring elsewhere), proanthocyanidins (prodelphinidins etc.), and special sulphuric sesquiterpene pseudoalkaloids present.

Systematics Nymphaeales and Schisandrales both have a quadrinucleate and quadricellular megagametophyte comprising a tricellular egg apparatus and a central cell with a single haploid polar nucleus at maturity (Friedman & Ryerson 2008). The two nuclei resulting from the first mitotic division of the single functional megaspore do not migrate to opposite regions of the developing megagametophyte, but remain at the micropylar pole. A second division produces four micropylar megagametophyte nuclei and the egg cell develops from one of these nuclei during the differentiation of the three-celled egg apparatus. The fourth cell forms the nucleus of the central cell and the endosperm resulting from the double fertilization becomes diploid.

Hydatellaceae (Trithuria) is sister to the clade [Nymphaeaceae+Cabombaceae]. Cabombaceae and Nymphaeaceae have rhizome. The tracheid end walls are provided with a unique reticulate fibrillar structure (at least in species of Nuphar and Nymphaea). The peltate leaves have an involute ptyxis (vernation) and palmate actinodromous or brochidodromous secondary veins. The flowers are borne singly on usually long scapes along the stem and possess a cortical vascular tissue. The tepals and stamens are whorled and the outer tepals enclose the remaining bud. The carpel margins are postgenitally fused and placentation is laminar. The exotesta is palisade and the anticlinal testal cell walls are sinuate.

The presence of hydropotes is a synapomorphy of at least Cabombaceae and Nymphaeaceae. It is not known whether they occur also in Trithuria (Hydatellaceae). Hydropotes are gland-like cellular structures on the abaxial leaf surface, responsible for the uptake of nutrients and water. A hydropote consists of a caducous unicellular or multicellular uniseriate portion which is abscised when mature, and a basal row of three or four partially overlapping epidermal cells (Carpenter 2006). In Cabombaceae the hydropotes are secretory with one or two terminal mucilaginous hair cells on top of two discoid cells and below these a basal foot cell. Carpenter (2006) interprets these structures as homologous with, e.g., (actinocytic/stephanocytic) stomata present in Amborella and Trimenia and the epidermal ethereal oil cell complexes of Schisandrales. Intermediates between true stomata, oil cell complexes and hydropotes are sometimes present.

Richard in J. B. G. M. Bory de Saint-Vincent, Dict. Class. Hist. Nat. 2: 608. 31 Dec 1822 [’Cabombeae’], nom. cons.

Hydropeltidaceae (DC.) Dumort., Comment. Bot.: 64. Nov-Dec 1822 [’Hydropeltideae’]

Distribution Cabomba: tropical, subtropical and temperate parts of North and South America; Brasenia: tropical, subtropical and temperate parts of North and Central America, the West Indies, Africa, East Asia (China, the Korean Peninsula, Taiwan, Japan, Manchuria), northern India, and northeastern and southeastern Australia.

Fossils Cabombaceae are known from the Early Cretaceous. Pluricarpellatia peltata is a Late Aptian to Early Albian Brazilian fossil with apocarpous gynoecium, suggesting affinity with Cabombaceae. Subfossils of Brasenia schreberi are described from a large number of localities in Europe and other parts of the Northern Hemisphere, and fossil leaves (Braseniopsis) resembling Brasenia are known from the Early Cretaceous of Portugal. Scutifolium jordanicum (Albian of Jordan) consists of peltate small leaves similar to Cabomba.

Habit Bisexual, perennial herbs. Aquatic, with rhizome and usually floating stem; submersed organs of Brasenia covered by a gelatinous layer (absent in Cabomba). Leaves of Brasenia isomorphous (monomorphous), in Cabomba anisomorphous (dimorphous).

Vegetative anatomy Mycorrhiza absent. Primary root ephemeral, replaced by adventitious roots, initiated from nodes (a single root arising from a point below each leaf); proximal cell comparatively small?; root cap enlarged?; secondary dermatogen present in root apex; root epidermis with short cells alternating with long cells; root endodermis with casparian strips and suberine lamels?; root aerenchyma interrupted by diaphragms. Phellogen absent. Epidermis initiated from outer cortical layer. Aerenchyma abundant. Stem with air canals and one to four vascular bundles (single or pairwise, collateral). Primary stem with scattered closed vascular bundles. Development of primary xylem mesarch? Axial vascular bundles concentric. Secondary lateral growth and cambium absent. Vessel elements (in Brasenia present in roots and stems; in Cabomba only in stems) – primary protoxylem lacunae – with perforation plates provided with series of pores or sometimes scalariform; tracheid end walls with reticulum of coarse fibrils; lateral cell wall thickenings annular to helical to scalariform (in root vessels unlignified), often inconspicuous, simple pits. Imperforate tracheary xylem elements tracheids with annular or spiral secondary cell wall thickenings and with simple pits. Wood rays absent. Axial parenchyma? Sieve tube plastids S type, with approx. ten starch grains. Sieve tube elements of primary phloem with almost transverse end walls and simple sieve plates. Nodes 1:2, unilacunar with two leaf traces; node anatomy difficult to interpret; in Cabomba one leaf trace initiated from each pair of vascular bundles, these immediately united commissurally and forming a nodal plexus. Laticifers present. Sclerenchymatous idioblasts and sclereids absent. Stems in Brasenia covered by thick mucilaginous layer. Starch grains complex. Prismatic calciumoxalate crystals often present in epidermal cells.

Trichomes Hairs tricellular or quadricellular, uniseriate, simple, in the form of secretory mucilage hairs, hydropotes, with a large terminal cell (in Brasenia).

Leaves Floating leaves in Brasenia alternate (spiral), simple, entire, usually peltate, with involute ptyxis, actinodromous venation, stomata and entire margin; specialized submerged leaves absent. Floating leaves in Cabomba alternate (spiral) or opposite (rarely verticillate), simple, entire or bifurcate, usually peltate, with involute ptyxis, actinodromous venation, stomata and entire margin (floating leaves few, developed at anthesis); specialized submersed leaves five- to seven-dissected, with each foliar part dichotomously or trichotomously branched, with stomata at margins near vein ends. Stipules adaxial bicarinate, pairwise lateral, or absent; leaf sheath absent. Petiole vascular bundle? Venation palmate, semidichotomous. Stomata stephanocytic or anomocytic, only on adaxial side of leaf, or absent. Cuticular waxes absent. Mesophyll with or without mucilage cells. Idioblasts with ethereal oils absent. Thin-walled spherical crystalliferous processes similar to oil cells often present on adaxial epidermis.

Inflorescence Flowers axillary or extra-axillary (arising laterally relative to leaf, with common vascular tissue), solitary (reduced raceme).

Flowers Actinomorphic, small. Hypogyny. Outer tepals (two or) three (or four), sepaloid, whorled, free (Brasenia) or connate at base (Cabomba); inner tepals (two or) three (or four), petaloid, whorled, free (Brasenia) or connate at base (Cabomba), with retarded development; tepals probably staminodial. Nectariferous spurs in Cabomba two adaxial at base of inner petaloid tepals; nectary absent in Brasenia. Disc absent.

Androecium Stamens three or six (Cabomba), or 18 to 36 (Brasenia), spiral or whorled. Filaments filiform, free from each other and from tepals. Anthers basifixed, non-versatile, tetrasporangiate, latrorse (Brasenia) or extrorse (Cabomba), longicidal (dehiscing with longitudinal slits). Tapetum amoeboid-periplasmodial (Cabomba), with migratory tapetal cells in direct contact with developing free microspores within anther locule. Staminodia intra- or extrastaminal.

Pollen grains Microsporogenesis simultaneous (Brasenia) or successive (Cabomba). Pollen grains boat-shaped, anasulcate (in Cabomba sometimes anatrichotomocolpate), shed as monads, bicellular (Cabomba) or tricellular (Brasenia) at dispersal. Exine tectate, with columellate infratectum, microperforate or scabrate (with rods, Brasenia) or striate (Cabomba); endexine not lamellate, initiated as plates.

Gynoecium Pistil composed of (one or) three (to seven) (Cabomba) or four to 19 (Brasenia) carpels, whorled, free (in Cabomba rarely connate at base); carpel ascidiate, with margins apparently occluded by secretion (carpel margins not fused). Ovary superior, unilocular (apocarpy). Style single, simple, short (Brasenia) or long (Cabomba). Stigma capitate (Cabomba) or deeply decurrent (Brasenia), papillate, Dry type. Pistillodium absent.

Ovules Placentation laminar-dorsal or laminar-median. Ovules usually two or three (sometimes one, four or five) per carpel, anatropous, pendulous, bitegmic, weakly crassinucellar. Micropyle endostomal (to bistomal?). Outer integument in Cabomba two, in Brasenia two to four cell layers thick. Inner integument two cell layers thick. Hypostase present. Megagametophyte in Cabomba (and Brasenia?) monosporous, quadricellular, Nuphar/Schisandra type. Antipodal cells ephemeral (Brasenia) or absent (Cabomba). Pollen tubes growing directly into dense substigmatic ground tissue subsequently reaching stylar canal through breakdown of mid-lamellae. Suspensor absent (proembryo with suspensor). Endosperm development helobial (first division transversal, micropylar cell free nuclear, chalazal cell enlarged). Endosperm haustorium chalazal. Embryogenesis asterad?

Fruit An assemblage of achenes (Brasenia) or dorsally dehiscent follicle-like fruits (Cabomba).

Seeds Aril absent. Operculum at micropylar end. Hilum and micropyle with common opening in centre of operculum. Seed coat mainly exotestal. Exotesta palisade, with sinuous anticlinal cell walls. Sclerotesta in Brasenia with very thick outer periclinal and anticlinal cell walls. Mesotesta and endotesta unspecialized. Tegmen unspecialized. Perisperm well developed, with multinucleate cells, starchy; starch grains compound. Endosperm sparse, little developed, enclosing embryo at micropylar end. Embryo small, slightly triangular, chlorophyll? Cotyledons two. Germination phanerocotylar? Radicula ephemeral.

Phytochemistry Hydrolyzable gallo- and ellagitannins (in Brasenia) present. Mucilage in Brasenia containing glucuronic acid, galactose, rhamnose, etc. Alkaloids not found.

Systematics Brasenia (1; tropical, subtropical and temperate parts of North and Central America, the West Indies, Africa, China, the Korean Peninsula, Taiwan, Japan, Manchuria, northern India, northeastern and southeastern Australia), Cabomba (5; C. aquatica, C. caroliniana, C. furcata, C. haynesii, C. palaeformis; tropical, subtropical and temperate parts of North and South America).

Cabombaceae are sister-group of Nymphaeaceae.

The vessel elements probably evolved in parallel in Nymphaeaceae and Cabombaceae (Schneider & Carlquist 1996).

Hydatellales Cronquist in Takhtajan, Bot. Rev. (Lancaster) 46: 317. 1980; Hydatellanae Takht. ex Reveal in Novon 2: 236. 13 Oct 1992

Distribution Western India, coastal areas in northern, southwestern and southern Australia, Tasmania, New Zealand.

Habit Usually monoecious (rarely dioecious), usually annual (rarely perennial) very small herbs. Caespitose aquatic and marsh plants. Trithuria inconspicua may flower at a depth of more than one metre.

Vegetative anatomy Mycorrhiza absent. Primary root early aborted, replaced by endogenous adventitious roots; air canals absent from roots and replaced by endodermis cells with large vacuoles. Phellogen absent. Epidermis initiated from outer cortical layer? Vessels – primary protoxylem lacunae – present in roots. Secondary lateral growth and cambium absent. Vessel elements with scalariform perforation plates; lateral pitting? Imperforate tracheary xylem elements? Wood rays absent. Axial parenchyma absent? Sieve tube plastids P2c type, with cuneate protein crystals, without starch or protein filaments. Nodes 1:1 (unilacunar with one leaf-trace)? Laticifers absent. Mucilage cells absent. Sclerenchyma absent. Calciumoxalate and silica probably absent.

Trichomes Eglandular hairs at stem bases only, axillary, uniseriate, multicellular (sometimes absent); glandular hairs (hydropotes?) with one to three basal cells and one elongate terminal (secretory?) cell present between flowers.

Leaves Alternate (spiral), simple, entire, linear to filiform, often in a basal rosette, with ? ptyxis. Stipules and leaf sheath absent. Petiole one-veined. Leaf with schizogenous air canal. Vein single, simple. Stomata anomocytic or absent. Cuticular waxes Strelitzia type or absent. Leaf margin entire. Vorläuferspitze (fore-runner point, apical precursor point) absent.

Inflorescence Terminal, capitate, cymose pseudanthia (possibly thyrse), surrounded by usually two or four (sometimes three or five, rarely six to eight) opposite, membranous, linear to tepaloid bracts. Inflorescence usually bisexual, with central centrifugally initiated male flowers surrounded by centrifugally initiated female flowers. Inflorescence hairs (hydropotes?) multicellular, with elongate (perhaps secretory) terminal cell. Floral prophylls (bracteoles) two, transversal (one of them sometimes undeveloped).

Flowers Actinomorphic, very small. Tepals absent. Pedicel at least sometimes articulated. Nectaries absent. Disc absent.

Androecium Stamen one. Filaments filiform. Anthers basifixed, non-versatile, tetrasporangiate, latrorse, longicidal (dehiscing by longitudinal slits). Tapetum? Staminodia absent.

Pollen grains Microsporogenesis simultaneous. Pollen grains boat-shaped, usually monosulcate (or indistinctly monoporate; occasionally trichotomosulcate), shed as monads, bicellular at dispersal. Exine tectate, with columellate infratectum, perforate, usually microechinate (sometimes striate).

Gynoecium Pistil composed of one in transverse section triangular carpel (or primarily three carpels forming a pseudomonomerous gynoecium); carpel ascidiate; carpel margins probably not fused (carpel seemingly ’closed’ by two compressed but not fused surfaces), at anthesis with a very short narrow canal. Closure by transverse slit occurring together with longitudinal slit. Ovary superior?, unilocular, briefly stipitate. Style absent. Stigma penicillate, consisting of two to ten uniseriate multicellular hairs, Dry type. Pistillodium absent.

Ovules Placentation apical. Ovule one per ovary, anatropous, apotropous, pendulous (with erect micropyle), bitegmic, pseudocrassinucellar or incompletely tenuinucellar. Micropyle bistomal. Outer integument two cell layers thick. Inner integument two cell layers thick. Nucellar cap ephemeral, formed by apical epidermis of megasporangium. Perisperm present outside megagametophyte in unfertilized ovules. Megagametophyte monosporous, quadrinucleate and probably quadricellular, Nuphar/Schisandra type; antipodal cells ephemeral or absent. Two megagametophytes often present in one and the same ovule (possibly developed from different megaspores in tetrad). Endosperm development ab initio cellular. Endosperm haustoria? Embryogenesis?

Fruit A one-seeded, thin-walled achenoid indehiscent follicle or a dehiscent follicle, dehiscing by three valves separating from three ribs. A single pericarp layer (exocarp) with except in regions adjacent to vascular bundles and at base and apex.

Seeds Aril absent. Operculum at micropylar end, with thickened tegmic cells (those adjacent to embryo strongly expanding during seedling growth). Seed coat mainly exotestal. Testa membranous, consisting of exotesta. Exotesta palisade; anticlinal cell walls not sinuous. Endotesta and exotegmen collapsing. Endotegmen tanniniferous. Perisperm well developed, rich in starch, formed subdermally from multicellular chalazal part of megasporangium. Endosperm few-celled, almost absent. Suspensor weakly developed or absent. Embryo small, peripheral, little differentiated, covered by operculum consisting of apical cells of inner layer of inner integument, chlorophyll? Cotyledons two, free from each other or fused through a leaf-like organ. Hypocotyl with collar rhizoids at base (rhizoids consisting of collar cells), developing asymmetrically. Germination cryptocotylar. Radicula ephemeral.

Systematics Trithuria (12; western India, coastal areas in northern, southwestern and southern Australia, Tasmania, New Zealand; T. konkanensis: western India; T. inconspicua: New Zealand; probably overlooked).

Trithuria (Hydatellaceae) is sister to the clade [Nymphaeaceae+Cabombaceae].

Trithuria shares numerous characters with especially Cabombaceae, but also Nymphaeaceae, several of which being unknown in Cyperales to which Hydatellaceae were formerly assigned. However, a number of these features also occur in different monocot clades. Cambium and pericyclic sclerenchyma are absent. The multicellular and probably secretory hairs present between stamens and carpels in Trithuria may be comparable to similar hairs in flowers of Brasenia. The stomata are anomocytic. The pollen grains are monosulcate and boat-shaped. The carpel is ascidiate, almost actinomorphic and similar to the early stages of the carpel in Cabomba. The ovule is anatropous and the megagametophyte develops according to the four-nucleate Nuphar/Schisandra type. The endosperm development is cellular. The exotesta is palisade and the outer integument is semi-annular (annular in, e.g., Barclaya). A seed operculum is formed by the enlargement of cells in the two-layered inner integument. The perisperm is usually early developed and rich in starch and the perisperm cells become multinucleate during their development. Also the weakly differentiated embryo in Trithuria is similar to certain Nymphaeales, having either a single cotyledon or possibly two fused cotyledons.

On the other hand, Trithuria has sieve tube plastids of P2c type (instead of S type as in Nymphaeaceae and Cabombaceae) and the leaves are linear. The ovule is tenuinucellar or pseudocrassinucellar (instead of crassinucellar). P2c type plastids also occur in Asaraceae (Asarum and Saruma). The linear leaves concentrated in a basal rosette and other superficial similarities between Trithuria and many monocotyledons – Cyperales in particular – may be due to adaptations to identical aquatic environments. The linear leaves in Trithuria resemble the first leaves of the seedling in Nymphaeaceae.

The inflorescence and flowers of Trithuria have been interpreted in several different ways. Is the gynoecium represented by a single ascidiate carpel or a pseudomonomerous pistil? The inflorescence consists of bracts which surround gynoecium and/or androecium, in bisexual units with the carpels outside the stamens. According to the interpretation by Rudall & al. (2007), the reproductive unit is an assemblage of apetalous unisexual flowers, each pistil thus corresponding to a solitary carpel.

In most species of Trithuria a bilobate membranous sheath (adnate to the testa) surrounds the main axis below the first seedling leaf. This sheath (reduced to a short outgrowth in some species) has been interpreted as homologous with the two connate cotyledons in Nymphaeaceae.

Salisbury in Ann. Bot. (König et Sims) 2: 70. Jun 1805 [’Nymphaeëae’], nom. cons.

Barclayaceae (Endl.) H. L. Li in Amer. Midl. Naturalist 54: 40. 27 Aug 1955; Euryalaceae J. Agardh, Theoria Syst. Plant.: 51. Apr-Sep 1858 [’Euryaleae’]; Nupharaceae A. Kern., Pflanzenleben 2: 699. 6-13 Jun 1891

Fossils Nymphaeaceae were previously much more diverse. Fossil Nymphaeaceae, flowers, seeds and leaf impressions, are known from Early Cretaceous (Turonian, c. 90 Mya) layers of, e.g., New Jersey. Monetianthus mirus is a 2 mm wide bisexual floral structure from the Late Aptian to the Early Albian of Portugal. Microvictoria svitkoana from the Early Cretaceous (possibly a species of Nymphaeaceae) may have belonged in the Nymphaeales stem group (Gandolfo & al. 2004). Its flowers are very similar to those in extant “Victoria” except for being approx. one tenth the size of the flowers in modern species. In “Victoria” the gynoecium is surrounded by ‘paracarpels’ also occurring in Microvictoria. The late Early Cretaceous aquatic Jaguariba wiersemana has been described from northeastern Brazil. Maastrichtian pollen grains of probable nymphaeacean origin have been found in Canada.

Habit Bisexual, usually perennial (rarely annual) herbs. Aquatic. Usually with rhizome or tuberous stem (some species of Nymphaea stoloniferous).

Vegetative anatomy Mycorrhiza absent. Radicula ephemeral, replaced by adventitious roots, initiated from nodes (one root arising from a point below each leaf). Proximal cell comparatively small; root cap enlarged; root apex with secondary dermatogen; root epidermis with short cells alternating with long cells; root endodermis with casparian strips; root aerenchyma interrupted by diaphragms. Inner root epidermis absent. Phellogen absent? Medulla of primary stem, rhizome, sometimes septate through diaphragms (with sclereids). Epidermis initiated from outer cortical layer. Rhizome with scattered closed vascular bundles; axial vascular bundles concentric. Stem vascular tissue complex near nodes. Maturation of primary xylem mesarch; primary xylem with tracheids (with annular, spiral or reticulate secondary cell wall thickenings) and protoxylem with lacunae. Secondary lateral growth and cambium absent. Vessels or vessel-like elements present in root primary xylem; vessel elements – primary protoxylem lacunae – with complex to scalariform perforation plates; pit membranes of root and stem tracheid end walls composed of coarse fibrils forming a meshwork (at least in Nuphar and some species of Nymphaea); lateral cell wall thickenings annular, helical or scalariform, simple pits. Imperforate tracheary xylem elements tracheids with simple pits. Wood rays absent. Axial parenchyma? Sieve tube plastids S type, with approx. ten starch grains. Nodes 3:3, trilacunar with three leaf traces. Trichoblasts in vertical rows and articulated unbranched laticifers abundant. Sclereids stellate to girdle- or H-shaped; asterosclereids with calciumoxalate crystals frequent in cell walls at least in Nuphar and Nymphaea, and also occurring in Barclaya. Starch grains complex. Tanniniferous parenchyma cells often abundant in rhizome.

Trichomes Hairs quadricellular, uniseriate, simple, on young organs often secretory (mucilaginous or nectariferous hairs) with large terminal cell, hydropotes.

Leaves Alternate (spiral), simple, entire, peltate or divided, with involute ptyxis, usually floating or submersed. Stipules adaxial and bicarinate or pairwise and lateral (Nymphaea), or absent (Nuphar, Barclaya); leaf sheath absent. Petiole vascular bundle? Venation palmate, actinodromous, brochidodromous. Stomata stephanocytic or anomocytic, on adaxial side of leaf only. Cuticular waxes absent. Mesophyll with sclerenchymatic idioblasts; asterosclereids present. Idioblasts with ethereal oils absent. Leaf margin serrate, sinuous or entire (in “Victoria amazonica” bent upwards by c. 90º).

Inflorescence Flowers axillary or extra-axillary, often not in normal axillary position, solitary (reduced raceme), with often very long pedicel, alternating with leaves in leaf spiral (Nuphar, Nymphaea, “Ondinea”) or arising from separate spirals from leaves (in the “Euryale” and “Victoria clades” of Nymphaea). Floral pherophylls (bracteoles and bracts) present in Nuphar.

Flowers Actinomorphic, often very large. Hypanthium usually present (absent in Nuphar). Hypogyny to epigyny. Tepals spiral, with imbricate aestivation, free (absent in some species of “Ondinea”), at least inner ones probably extrastaminal staminodia; outer (two to) four to six (to twelve) tepals sepaloid to petaloid; inner two to more than 70 tepals (rarely absent) usually petaloid staminodia with nectaries. Disc absent.

Androecium Stamens 14 to more than 200, spiral or whorled, foliaceous, three-veined, free, outwards and inwards often grading into staminodia. Anthers basifixed, non-versatile, tetrasporangiate, usually introrse (rarely latrorse), longicidal (dehiscing usually with longitudinal slits, in Nuphar H-shaped); connective present or absent. Tapetum usually secretory (in Nuphar amoeboid-periplasmodial). Staminodia often numerous.

Pollen grains Microsporogenesis simultaneous. Pollen grains usually globose (in Nuphar boat-shaped), usually zonasulculate (with band-like aperture encircling equator; in Nuphar anasulcate; in Barclaya inaperturate), usually shed as monads (in the “Victoria clade” of Nymphaea as tetrads), tricellular (or bicellular?) at dispersal. Exine tectate, with granular to intermediary infratectum; tectum in Nymphaea psilate, spinulate or verrucate, in Nuphar and the “Euryale clade” of Nymphaea echinulate or spinulate, in Barclaya psilate or scabrate.

Gynoecium Pistil composed of three to c. 35 conduplicate carpels, whorled, laterally partially or entirely connate (receptacle often intruding into centre); carpel usually ascidiate (in Barclaya plicate to intermediate due to expanding central floral parts), postgenitally fused, with secretory canal; extragynoecial compitum present in Nymphaea. Ovary superior to inferior, plurilocular. Style absent or (in Barclaya and most species of Nymphaea) transformed into carpellary appendages. Stigma capitate, papillate (with unicellular or multicellular papillae), in Nuphar Wet and in Nymphaea usually Wet type (in the “Victoria” and “Euryale clades” and in Barclaya Dry type), with receptive surfaces radiating from centre (either on expanded apical disc or along cupular ovary surface; in Barclaya as indistinct radial disc with central conical appendage).

Ovules Placentation laminar-diffuse. Ovules (three to) numerous per carpel, usually anatropous, pendulous (in Barclaya orthotropous, horizontal and radially-laterally arranged), bitegmic, crassinucellar (in Barclaya weakly crassinucellar). Micropyle bistomal or endostomal. Outer integument cupular, two to numerous cell layers thick (in Barclaya two; in the “Euryale clade” of Nymphaea up to c. 20 cell layers thick). Inner integument two cell layers thick. Chalaza sometimes pachychalazal. Nucellar cap present in Nuphar. Megagametophyte monosporous, quadrinucleate, Nuphar/Schisandra type. Pollen tubes growing through short substigmatic zone, consisting of fused ground tissue, prior to reaching stylar canal. Endosperm development usually cellular (in some species of Nymphaea helobial; in the “Euryale clade” of Nymphaea nuclear). Endosperm haustorium chalazal. Embryogenesis asterad.

Fruit A berry-like capsule with fleshy spongy tissue, dorsally to irregularly dehiscing by expansion of mucilage in ovary locules.

Seeds Seeds in Nymphaea with funicular aril (absent in Barclaya and Nuphar) and at micropylar end an apical hood-shaped operculum dehiscing at germination; hilum present outside operculum. Seed coat exotestal. Exotesta often palisade (in Barclaya with special hairs), with sinuous anticlinal cell walls. Mesotesta and endotesta unspecialized. Tegmen unspecialized. Perisperm well developed, usually copious, with multinucleate cells, with compound starch grains, or absent. Endosperm scarce, little developed, enclosing embryo at micropylar end. Suspensor absent. Embryo small, wide, slightly triangular, well differentiated, with or without chlorophyll. Cotyledons two, thick and fleshy, often fused. Germination phanerocotylar. Radicula ephemeral.

Cytology Barclaya, Nuphar: n = 17, 18; Nymphaea: n = (10–)14–112 (“Victoria clade”: n = 10, 12; “Euryale clade”: n = 29) – Polyploidy occurring at least in Nymphaea.

DNA An intergenic inversion of c. 200 bp is present in the plastid inverted repeat.

Phytochemistry Flavonols (kaempferol, quercetin, myricetin), flavone-C-glycosides, ellagic and gallic acid, hydrolyzable gallo- and ellagitannins (unique ellagitannins in Nuphar, Nymphaea), proanthocyanidins (prodelphinidins etc.), and special sulphuric sesquiterpene pseudoalkaloids present. Benzylisoquinoline alkaloids?

Use Ornamental plants, aquarium plants (Barclaya longifolia etc.), edible seeds.

Systematics Nymphaeaceae are sister-group of Cabombaceae and Nuphar is sister to the clade [Barclaya+Nymphaea]. Barclaya is sister to an extended Nymphaea.

Nuphareae Endl., Gen. Plant.: 900. Nov 1839 [‘Nupharinae’]

Nuphar (c 20 [7–25]; North America, Europe, East Asia). – Roots with ten to 18 xylem poles. Pith extensive. Petiole and pedicel with numerous narrow air canals. Hypogyny. Outer (sepaloid) tepals five to 14, spiral. Distal part of gynoecium forming a more or less flattened disc with rays of stigmatic tissue. Stamens numerous. Staminodia absent. Pollen grains spinulate. Carpels five to 23 (to 30). Seeds non-arillate.

Nymphaeeae DC., Syst. Nat. 2: 43, 48. late Mai 1821

2/55–70. Nymphaea (c 50–65; almost cosmopolitan; “Ondinea clade“: northern Western Australia; “Victoria clade“: northern and central South America; “Euryale clade“: northern India, China, Japan), Barclaya (4; B. kunstleri, B. longifolia, B. motleyi, B. rotundifolia; Southeast Asia, Malesia). – Roots with five to nine xylem poles. Pith not extensive. Petioles and pedicels in Nymphaea s.lat. with few wide (in Barclaya numerous narrow) air canals. Inner satellite peduncular vascular bundle present. Epigyny or half epigyny. Outer (sepaloid) tepals (three or) four (or five), spiral. Stamens (14 to) numerous. Staminodia well developed, large, showy, or absent. Pollen grains zonasulcate (to inaperturate), with various supratectal sculpturing (filaments in the “Euryale clade” of Nymphaea thin and adnate at base to staminodia). Carpels (three to) eight to numerous. Stigmatic surface continuous. Placentation usually laminar. Ovules in Barclaya orthotropous. Fruits ripening below water surface. Seeds arillate (seeds in Barclaya echinate, non-arillate; exotestal cells in the “Euryale clade” of Nymphaea cuboid). x = 10, 12, 14–18. Polyploidy occurring. – The aril in Nymphaea has evolved into a floating device for the seed.

Cladogram of Nymphaeaceae based on DNA sequence data and morphology (Les & al. 1999; Löhne & al. 2007; Borsch & al. 2008). The former genera Euryale, Ondinea and Victoria are nested deep inside Nymphaea.

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NYMPHAEIDAE J. W. Walker ex Takht.

NYMPHAEALES Salisb. ex Bercht. et J. Presl

CABOMBACEAE Rich. ex A. Rich.

HYDATELLACEAE U. Hamann

NYMPHAEACEAE Salisb.