Discussion (Ken Friedman @1980)
R. prismatica, R. tetragona, R. heteroclada, R. suareziana
R. prismatica Rumpler was described by Rose as "much-branched, prostrate; lower branches elongated and terete; upper branches short and somewhat angled. . .flowers white; petals usually 5; obtuse; fruit small, pinkish-to-white, globose (p. 233)." Distribution was reported as Brazil and northern Madagascar, rather a wide separation, with range unknown. Rose reported that Weber thought R. tetragona was the same as R. prismatica, but because he was not certain he described it as new.
Rose also reported a then new species, R. heteroclada, which he described in detail in the table. He wrote that the plant was very common in Brazilian collections.
Barthlott (1977b) said that R. prismatica was a juvenile form of R. heteroclada, having based his observation on field specimens of the latter, which reverted to the former's characteristics when grown at the University of Heidelberg. Although R. heteroclada specimens are "older," the name R. prismatica itself is older and thus has precedence. It appears that the name R. prismatica will remain, while R. heteroclada will be dropped. A New York Botanical Garden specimen, originally labelled R. teres, was tentatively identified as R. heteroclada by Barthlott during a visit in August 1977. He said, when I visited the NYBG with him, that he based his judgement on vegetative characteristics. A cutting of the New York specimen flowered for me in January 1978 and was distinctly a dull white with a dried blood color showing prominantly, especially on the petal tips.
Rose also referred R. suareziana Weber to R. prismatica. Guillaumet (1972), reporting on variations in the genus Rhipsalis from Madagascar, referred to "R. suareziana living on rocks along the dry west coast"--the same reference that Rose had made to R. prismatica 49 years earlier. Udalova (1976 ) reported cotyledon research on "R. suariziana" but the Russian was beyond my understanding. All that I can conclude is that there are specimens of Rhipsalis from Madagascar passing under this name.