Lepismium cruciforme var. cavernosum (Lindbg.) Backbg.
Treated as a synonym of L. cruciforme by B&T in Bradleya 13
Desc from Backeberg 1977
Flowers translucent white
R Knightii (Knight's) - Stems and joints as in R. commune.
Detail from Cactus Culture – Watson 1889: Wings of joints usually broad, with red margins, and the hair in the notches in a dense tuft, nearly 1 in. long, pure white, and silklike. Flowers small, white. This species, which thrives best under warm-house treatment, is a native of Brazil, and is usually grown only for its curious, Cereus-like stems. It forms a straggling plant about 1 ft. high. Syn. Lepismium Knightii, Cereus Knightii.