Trichocereus peruvianus Br. et R. = Cereus roseii Werd. peru. plant 2 to 4 m. high. much branched, with stems 6 to 10 cm. thick, erect or prostrate, bluish green passing to green or dull greyish green, with 6 to 8 ribs, and brownish areoles about 2 1/2 cm apart. Spines about 10, brownish up to 4cm long. flowers 22 to 25 cm. long white, sweet scented. The name Roseii was given by Werdermann to distinguish it from cereus (piptanthocereus) peruvianus. Very similar to T. macragonus, but usually more slender and often prostrate. from J.Borg Cacti Third edition 1959 But actually it's called Echinopsis peruviana (B+R) FrdH+Rowl 1974 from the new cactus lexicon 2006 There's no point arguing over old names.