Rhizomes from erect short shoots or other rhizomes; vascular plexus at nodes, stomata [on floating leaves] parallel to the veins; short shoots with cataphylls, submerged leaves opposite or 3-whorled, lamina deeply palmately (subdichotomously) dissected, lobes linear; flowering shoots long shoots, from erect shoots or rhizomes, monopodial (becoming sympodial); flowers initially axillary; T in a single whorl, inner T somewhat delayed in development, nectaries +, trichomatous; A 3 [opposite inner T], 6 [alternating with T], extrorse; pollen trichotomocolpate, tectum continuous, striate; G 1-4(-7), (basally connate), style becoming hollow [lysigenous], stigma capitate; fruit follicular; seeds 2-3, spiny; n = 13.

(Mycorrhizae +); (rhizome +, short, erect); phloem loading active, cell walls smooth, no plasmodesmata; roots with 5-9 xylem poles, pith at most small; stomata parallel [?orientation]; vegetative buds not axillary; lamina peltate to cordate/hastate, (margin serrate), (prickles on lower surface, pedicel, etc.); stipules +, adaxial and bicarinate or lateral/0; growth ?sympodial, peduncle at base with one bundle, inner satellite bundle +; bract 0 (+ - Victoria); hypanthium developed; P members 3-veined, "K" 4-5, spiral/quincuncial, abaxial K first initiated, (apex hooded/"long aristate" - Barclaya [B.]), "C" (0 - some Ondinea - O.), (basally connate - B.), intermediates between A and "C"; A (15 - O), (latrorse - O.), (adnate to "C"), (outer staminodes +, showy, inner staminodes [= paracarpels] + - V.); (staminal bundle unbranched, esp. in smaller inner A); pollen (in tetrads), bi/tricellular, (globose), with encircling sulcus [zonasulcate], (inaperturate), surface various, inc. tectum continuous, infratectal space usu. small, columellae inconspicuous; G 3-many, inferior [A alone on top of G, also often K and C], with inter-carpellary septal slits, marginal appendages + [= pseudostigmas/carpellary styles]/(0), central pool of stigmatic fluid, floral axis projecting in the middle (not - B.), stigmatic surface continuous, (not - O); ovules (straight - B.), (micropyle bistomal), outer integument (2[B.]) 4-5, ca 20 cells across [Euryale], (parietal tissue 3-4 cells across - V. ); embryo sac hour-glass shaped [N. thermarum]; fruit maturing submerged; seeds arillate (not, surface spiny - B.); exotesta mucilaginous [?level], (cells cuboid, anticlinal walls straight - E.); (embryo suspensor 0); n = 10, 12, 14-18, nuclear genome [1 C] 450-4557 Mbp; seedlings with hastate leaves.

Evolution: Divergence & Distribution. The family is thought to have been much more diverse in earlier epochs, distinctive seeds with a micropylar and palisade exotesta with sinuous anticlinal walls that can be assigned here being common in the Cretaceous (Friis et al. 2009b, 2011, 2017b; see also above). Recently, fossils assigned to crown group Nymphaeaceae (as Jaguariba) have been found in the Aptian Crato flora, some 115 Ma in northeast Brazil (Coiffard et al. 2013a) and the first seeds from the Southern Hemisphere have been described in Eocene deposits from Seymour Island, Antarctica (Friis et al. 2017b).

Barclaya rotundifolia is a terrestrial plant of wet forests in western Malesia.

Pollination Biology & Seed Dispersal. Thermogenesis has been detected in the flowers of some Nymphaeaceae (Prance & Arias 1975: ca 9.5o in Victoria; Seymour 2001; Seymour & Matthews 2006). Beetles and a variety of other insects, including bees and flies, are pollinators (e.g. Gandolfo et al. 2004; Padgett 2007; Thien et al. 2009; Zini et al. 2019). Scarab beetles (Cyclocephalini) may have pollinated night-flowering water lilies for some 100 My; they pollinate species both in America, where the beetles are common, and in Africa, where the beetles are otherwise very uncommon (Ervik & Knudsen 2003; Moore & Jameson 2013); beetle pollination may have occurred even in the early small-flowered members of the family (M. L. Taylor et al. 2013 and references). The marginal carpellary appendages of the flowers in Nymphaeaoideae function as osmophores in both day- and night-flowering taxa (in Nymphaea s. str. and Victoria, e.g. L. T. Smith et al. 2022) that are pollinated by deceit - beetles and bees (also visual cues in the latter) are involved (Zini et al. 2019); Prance and Arias (1975) suggested that in Victoria amazonica the beetles ate the carbohydrate-rich marginal appendages. The distinctive flowers of Ondinea (= Nymphaea ondinea), wind pollinated (evidence for this?), are derived from Nymphaea-type flowers (L?hne et al. 2009). E. L. Schneider (1979) summarized information about the pollination biology of the family; see also Erbar (2014), Gottsberger (2016: Table 2, much detail), Luo et al. (2018) and Coiro and Barone Lumaga (2018: floral epidermal micromorphology).

The progamic phase, the time between pollination and fertilization, is notably short, up to a mere 8 hours, as in at least some other aquatic angiosperms (including Nelumbo: see Williams et al. 2010).

The fruit of Nymphaeoideae splits open as the mucilage inside (from arils? - L. T. Smith et al. 2022) swells, whereupon the wall splits irregularly; as Jacobsen et al. (2022: p. 14) described the process for Barclaya (which has spiny seeds) "At full maturity the pericarp ruptures, and the spongy substance surrounding the seeds quickly swells, enabling the embedded seeds to spread on the water surface". The newly-released seeds in Victoria s. str. at least initially float (Smith et al. 2022). Romanov et al. (2023) described the individual carpels of Nuphar as being the initial disseminule unit, however, since the outer part of the pericarp fell off irregularly, the fruits could not be called a schizocarp.

Plant-Animal Interactions. Nymphaeaceae are host plants of reed beetles, Chrysomelidae-Donaciinae (see also Poales: K?lsch & Pedersen 2008: much discussion on the age and evolution of the group). Enterobacteriaceae near Buchnera are thought to produce the material that makes up the cocoon that characterises Donaciinae, a group that is also noted for the ability of the larvae to grow under water (K?lsch & Pedersen 2010).

Genes & Genomes. A genome duplication in Nuphar is estimated to have occurred (76.8-)72.8(-67.9) Ma (Vanneste et al. 2014b) and one in Euryale ferox at 106-94 Ma (Y. Yang et al. 2020); it is pegged at the level of [Nymphaea + Nuphar] and dated to around 106.3 Ma (Landis et al. 2018: App. S1), so its extent depends on confirmation of the position of Nuphar... See also L. Zhang et al. (2019) for this/another duplication, while L. Zhang et al. (2020) date what is called the pie/pi duplication to (120-100(-98) Ma and X. Guo et al. (2021) date it to 119.8-85.8 Ma.

For chloroplast organisation, etc., see He et al. (2018). Interestingly, Nuphar has the highest number of short tandem repeats (>50), followed by Barclaya (>30), and Nymphaea as few as 19 (He et al. 2018).

Economic Importance. Nymphaeaceae include a disproportionally high number of serious and widespread weeds (Daehler 1997).