Nymphaea // (water lily) is a genus of hardy and tender aquatic plants in the family Nymphaeaceae. There are about 50 species in the genus, which has a cosmopolitan distribution. White-flowered waterlilies (of several species) are the national flower of Bangladesh.
The name Nymphaea comes from the Greek term "Νυμφαία", possibly related to "Νύμφη" meaning "nymph". The nymphs in Greek mythology were supernatural feminine beings associated with springs, so the application of the name to delicately flowered aquatic plants is understandable. Despite its common name "water lily" (water-lily, waterlily), Nymphaea is not related to the true lily, Lilium.
The main plant is submerged, with large floating, plate-like leaves and showy flowers in many different colours produced in spring. Blue flowers are only produced by the tender species, e.g. N. caerulea. The fruits, containing many seeds, are produced in the autumn, and are also submerged. The leaves have a radial notch from the circumference to the petiole (leaf stem) in the center.
Nymphaea (Egyptian lotus) is not related to the Chinese and Indian lotus of genus Nelumbo. But it is closely related to Nuphar, another genus commonly called "lotus". In Nymphaea, the flower petals are much larger than the sepals, whereas in Nuphar the petals are much smaller than its sepals. The fruit maturation also differs, with Nymphaea fruit sinking below the water level immediately after the flower closes, whereas Nuphar fruit are held above water level to maturity.
Cultural significance 
The Egyptian Blue Water-lily, N. caerulea, opens its flowers in the morning and then sinks beneath the water at dusk, while the Egyptian White Water-lily, N. lotus, flowers at night and closes in the morning. This symbolizes the Egyptian separation of deities and is a motif associated with Egyptian beliefs concerning death and the afterlife. The recent discovery of psychedelic properties of the blue lotus may also have been known to the Egyptians and explain its ceremonial role. Remains of both flowers have been found in the burial tomb of Ramesses II.
A Syrian terra-cotta plaque from the 14th-13th century B.C.E. shows the goddess Asherah holding two lotus blossoms. An ivory panel from the 9th-8th century B.C.E. shows the god Horus seated on a lotus blossom, flanked by two Cherubs.
Water-lilies are not only highly decorative, but provide useful shade which helps reduce the growth of algae in ponds and lakes. Many of the water-lilies familiar in water gardening are hybrids. The following cultivars have gained the Royal Horticultural Society's Award of Garden Merit:-
- 'Escarboucle' (orange-red)
- 'Gladstoniana' (double white flowers with prominent yellow stamens)
- 'Gonnère' (double white scented flowers)
- 'James Brydon;' (cupped rose-red flowers)
- 'Marliacea Chromatella' (pale yellow flowers)
- 'Pygmaea Helvola' (cupped fragrant yellow flowers)
Other Uses 
Water lilies have several edible parts. The young leaves and unopened flower buds can be boiled and served as a vegetable. The seeds, high in starch, protein, and oil, may be popped, parched, or ground into flour. Potato-like tubers can be collected from the species N. tuberosa.
Subdivisions of genus Nymphaea:
- A Hossain, G Kabir, M M Ud-deen, and A M S Alam (2007). "Cytological studies of Nymphaea species available in Bangladesh". Journal of Bio-Science 15: 7–13.
- William G. Dever; Did God have a Wife? Archeology and Folk Religion in Ancient Israel; page 221, 279.
- RHS A-Z encyclopedia of garden plants. United Kingdom: Dorling Kindersley. 2008. p. 1136. ISBN 1405332964.
- Peterson, Lee Allen (1977). A field guide to the wild edible plants of Eastern and Central North America. New York, New York: Houghton Mifflin. p. 22.
- "Nymphaea L.". USDA GRIN Taxonomy.
- Perry D. Slocum: Waterlilies and Lotuses. Timber Press 2005, ISBN 0-88192-684-1 (restricted online version at Google Books)
- Kit Notts, "The first hybrid waterlilies"
- Species of Nymphaea subgenus Hydrocallis (species as recognized by GRIN)
|Wikimedia Commons has media related to: Nymphaea|