Autor: Miller

“Wax candle”, referring to the cylindrical stems of this genus, having the shape of a wax candle.
Shrubby or treelike plants, usually much branched, erect or prostrate depending on the species and often with a welldefined trunk. Stems angular, ribbed and well developed, with rather large areoles, generally woolly but not hairy. Spines often numerous and aciculate. Pseudocephalium densely woolly, present in only one species, Cereus mortensenii.
Flowers nocturnal, funnel-shaped, white, whitish purple or yellow, pollinated by Sphingidae (Cereus aethiops, C. fernambucensis, C. hildmannianus), bats (Glossophagasoricina, G. longirostris and Leptonycteris curasoae for Cereus repandus; Artibeus iituratus, A. jamaicensis and Glossophaga longirostris for Cereus hexagonus) during the night, and hummingbirds (Chlorostiibon aureiventris for C.jamacaru) when they are still open in the morning. Fruits globose to ovoid, fleshy, with a lateral dehiscence, highly variable in colour, may be greenish, yellow, red or bluish, keeping or not keeping the remains of dried perianth. Seeds large, black, rough, strongly tuberculate. Seed dispersal (for Cereus stenogonus and probably many others) provided by – among others and in some areas – the tapir (Tapirus terrestris).
As circumscribed here, the genus Cereus grows in a variety of habitats (some species such as C. validus having a wide distribution), mainly in the shade, in thorny thickets and dry forests of South America, also in full sun on rocky hills of volcanic origin (C. insularis), plains, on various soils, granitic, sandy, etc., almost from the sea level up to 3200 m in altitude.
Argentina (Buenos-Aires, Catamarca, Chaco, Cordoba, Corrientes, Entre Rios, Jujuy, La Pampa, La Rioja, Mendoza, Misiones, Rio Negro, Salta, San Juan, San Luis, Tucuman), Bolivia (Beni, Cochabamba, Santa Cruz,), Brazil (Alagoas, Bahia, Ceara, Espirito Santo, Goias, ile Fernando de Noronha, Maranhao, Mato Grosso, Minas Gerais, Paraiba, Parana, Pernambuco, Piaui, Rio de Janeiro, Rio Grande do Norte, Rio Grande do Sul, Santa Catarina, Sao Paulo, Sergipe, Tocantins), Colombia, Ecuador (Guayas, Los Rios), Guyana, French Guyana, Caribean Islands (Grenada, Trinidad & Tobago), Paraguay (Chaco, Cordillera, Guaira, Paraguari), Peru (Apurimac, Cuzco, Loreto, San Martin), Surinam, Uruguay (Colonia), Venezuela (Lara).

Currently 26 species of which some are doubtful + 3 subspecies
– Cereus aethiops* Haw. 1830
– Cereus albicaulis (Britton & Rose) Luetzelb. 1923
– Cereus bicolor Rizzini & A.Mattos 1985
– Cereus braunii Cárdenas 1956
– Cereus cochabambensis Cárdenas 1970
– Cereus colosseus (F.Ritter) Guiggi 2012
– Cereus comarapanus Cárdenas 1956
– Cereus fernambucensis Lem. 1839
– Cereus fernambucensis subsp. sericifer (F.Ritter) N.P.Taylor& zappi 1997
– Cereus fricii Backeb. 1930
– Cereus grenadensis Britton & Rose 1920
– Cereus hankeanus F.A.C.Weber ex K.Schum. 1898
– Cereus hexagonus (L.) Mill. 1768
– Cereus hildmannlanus* K.Schum. 1890 (= C. alacriportanus ?)
– Cereus hildmannianus subsp. uruguayanus (R.Kiesiing) N.p.Tayior 1998
– Cereus horrispinus Backeb. 1930
– Cereus huilunchu Cárdenas 1951
– Cereus insularis Hemsl. 1884
– Cereus jamacaru* DC. 1828
– Cereus jamacaru subsp. calclrupicola (F.Ritter) N.P.Tayior & Zappi 1997
– Cereus lanosus (F.Ritter) P.J.Braun 1988
– Cereus mirabella N.P.Tayior 1991
– Cereus mortensenii (Croizat) D.R.Hunt & N.P.Tayior 1991
– Cereus pierre-braunianus Esteves 2003
– Cereus repandus ( L . ) Mill. 1768
– Cereus stenogonus K.Schum. 1899 (= C. dayamii)
– Cereus trigonodendron K.Schum. ex Vaupel 1908
– Cereus validus Haw. 1831
– Cereus vargasianus Cárdenas 1951

References: "TAXONOMY of the CACTACEAE" -  ISBN 978-84-617-3723-9 (Vol. 1)