An order of flowering plants that have previously been included in the same larger grouping as Magnoliales, the Magnoliidae. Deoxyribonucleic acid (DNA) sequence studies have demonstrated that Nymphaeales as previously defined contain two families, Ceratophyllaceae (water hornwort) and Nelumbonaceae (lotus), that are not closely related to the others. Remaining in the order is the family Nymphaeaceae, the waterlilies, from which a small group of tropical plants, Cabombaceae, are split by some scientists. Nymphaeaceae contain nearly 100 species of fresh-water aquatics that are typically found in river and lake systems throughout the world. The ovaries of these plants are filled with mucilage, which mediates pollen tube growth from the stigmas to the ovules, and they have either inappertuate or monosulcate pollen. A spectacular plant is the Amazonian water lily (Victoria), which has leaves up to 15 ft (5 m) in diameter. The water lily family has been shown by deoxyribonucleic acid analyses to be one of the oldest lineages of flowering plants and distantly related to all others as well. The family members are relics of the early diversification of the flowering plants.