Najas
Najas, the water-nymphs or naiads, is a genus of aquatic plants. It is cosmopolitan in distribution, first described for modern science by Linnaeus in 1753. Until 1997, it was rarely placed in the Hydrocharitaceae, and was often taken as constituting the family Najadaceae.
The APG II system, of 2003, places the genus in family Hydrocharitaceae, in the order Alismatales of the monocots.
An infrageneric classification of two sections is proposed: Section Americanae and sect. Caulinia.
;SpeciesNajas affinis Rendle - South America, Senegal, Guinea-BissauNajas ancistrocarpa A.Braun ex Magnus - China, Japan, TaiwanNajas arguta Kunth - Cuba, Costa Rica, Panama, South AmericaNajas australis Bory ex Rendle - India, Madagascar, Mauritius, KwaZulu-Natal, SeychellesNajas baldwinii Horn - West AfricaNajas brevistyla Rendle - AssamNajas browniana Rendle - southern China, India, Taiwan, Java, Cavern Island in Northern Territory of AustraliaNajas chinensis N.Z.Wang - Primorye, China, Taiwan, JapanNajas conferta A.Braun - Cuba, Hispaniola, Panama, BrazilNajas faveolata A. Br. ex MagnusNajas filifolia R.R.Haynes - southeastern United States Najas flexilis Rostk. & W.L.E. Schmidt - temperate Northern HemisphereNajas gracillima Magnus - Asia, North AmericaNajas graminea Delile - Africa, Asia, New Guinea, Melanesia, northern Australia; naturalized in California and parts of EuropeNajas grossareolata L.Triest - Sri LankaNajas guadalupensis Magnus - North and South America, CaribbeanNajas hagerupii Horn - Ghana, MaliNajas halophila L.Triest - Java, New Guinea, QueenslandNajas heteromorpha Griff. ex Voigt - eastern IndiaNajas horrida A.Braun ex Magnus - Africa, Madagascar, SinaiNajas indica Cham. - Indian Subcontinent, China, Southeast Asia, New GuineaNajas kurziana Rendle - Bihar, East TimorNajas madagascariensis Rendle - Madagascar; naturalized in MauritiusNajas malesiana W.J.de Wilde - India, Bangladesh, Indochina, Malaysia, Indonesia, Philippines; naturalized in eastern BrazilNajas marina L. - widespread and nearly cosmopolitanNajas minor All. - widespread in Europe, Asia, Africa; naturalized in eastern North AmericaNajas oguraensis Miki - East Asia, Himalayas Najas pectinata Magnus - SaharaNajas pseudogracillima L.Triest - Hong KongNajas rigida Griff. - eastern IndiaNajas schweinfurthii Magnus - Senegal, Cameroon, Ethiopia, Sudan, Tanzania Najas tenuicaulis Miki - Honshu Island in JapanNajas tenuifolia R.Br. - Hong Kong, Southeast Asia, AustraliaNajas tenuis Magnus – India, Sri Lanka, MyanmarNajas tenuissima Magnus - Finland, Russia, HokkaidoNajas testui Rendle - western + central AfricaNajas welwitschii Rendle - tropical Africa, western IndiaNajas wrightiana A.Braun - Mexico, Central America, Cuba, Bahamas, Venezuela; naturalized in Florida