Cleistocactus is a genus of flowering plants in the cactus family Cactaceae, native to mountainous areas - to - of South America (Peru, Uruguay, Bolivia and Argentina). The name comes from the Greek kleistos meaning closed because the flowers hardly open. The stems of these cacti are tall, mostly slender and often many-branched with numerous ribs with closely set areoles and spines. The flowers are tubular and the tips hardly open with only the style and stamens usually protruding. Species Natural Hybrids Cleistocactus × crassiserpens Rauh & Backeb.(Cleistocactus icosagonus × Cleistocactus serpens). Synonyms The following genera have been brought into synonymy with this genus: Akersia Buining Bolivicereus Cárdenas Borzicactella H.Johnson ex F.Ritter Borzicactus Riccob Borzicereus Fric & Kreuz. (orth. var.) Cephalocleistocactus F.Ritter Cleistocereus Fric & Kreuz. (orth. var.) Clistanthocereus Backeb. Demnosa Fric Gymnanthocereus Backeb. Hildewintera F.Ritter Loxanthocereus Backeb. Maritimocereus Akers Pseudoechinocereus Buining (nom. inval.) Seticereus Backeb. Seticleistocactus Backeb. Winteria F.Ritter Winterocereus Backeb. References Innes C, Wall B (1995). Cacti, Succulents and Bromaliads. Cassell & The Royal Horticultural Society. The species list is referenced from http://www.cactiguide.com/ which is in turn referenced from several books which are listed on that site. The principal book listed here is The Cactus Family by Edward F. Anderson. External links photos on www.AIAPS.org photos on www.cactiguide.com Trichocereeae Cacti of South America Flora of Argentina Flora of Bolivia Flora of Peru Flora of Uruguay Cactoideae genera