Aquatic, usually large, perennial herbs with milky latex and stout creeping rhizome bearing roots at the nodes. Leaves alternate, peltate, floating on the water surface when immature, raised high above the water surface when mature, petiole very long upto 2 m, bearing numerous spines, lamina usually reniform to orbicular, glaucous with upturned margin, prominently veined from the centre. Flowers large, pinkish red, white or yellow. Perianth segments 14 to 30; outer 2-5 persistent and sepal-like, often regarded as sepals; inner caduceus. Stamens numerous (many senate), caducous, usually with conspicuous fleshy appendages. Pollen tricolpate, carpels several, borne singly in the cavities of the broad, turbinate, spongy receptacle; stigma terminal, ± peltate. Fruit a hard walled nut.
A unigeneric family with 2 species; 1 species distributed in the West Indies, C. America, Southern and Eastern parts of N. America and the other in S. E. Asia, India, Pakistan and Iran. The genus Nelumbo has previously been included in the family Nymphaeaceae. However, Dumotier (Fam. Pl. 2: 76. 1763) recognized a separate family Nelumbonaceae on the basis of the seeds with large embryo and abundant endosperm. However, the latter workers like Bentham & Hooker and even the recent workers like Hutchinson (Fam. Fl. Pl. 1: 403-404. 1960) treated Nelumbo under Nymphaeaceae. Cronquist (Evot & Class. Fl. Pl. 150. 1968) accepted two separate families but still keeping under one order Nymphaeales. Takhtajan (Fl. Pl. Orig. & Disp. 207. 1969) created a separate order Nelumbonales and showed that it differed from Nymphaeales in many important features including the tricolpate pollen grains, the structure of embryo, the presence of special respiratory openings in the pericarp and seed coat, the absence of lactiferous tubes and idioblasts and the morphology of chromosomes. Nelumbonales shows a more probable link with Illiciales - Ranunculales stock rather than Nymphaeales.
Acknowledgements: We are grateful to Prof. C.D.K. Cook and Dr. M. Wolf (Botanisher Garten and Institute Cur Systematische Botanik der Universitat Zurich, Switzerland) for going through the manuscript and offering valuable suggestions. The financial assistance received from the United States Department of Agriculture under P.L. 480 with the coordination of Pakistan Agricultural Research Council, Islamabad is thankfully acknowledged.
