DISTRIBUTION   Peru (San Martin), Ecuador (Napo, Morona-Santiago, Zamora-Chichipe), Suriname: epiphyte in perhumid equatorial forest, to c. 950 m altitude. 

This taxon is probably closely related to R. micrantha, but in contrast is very difficult to maintain in cultivation, which also distinguishes it from the superficially similar Brazilian species, R. oblonga.

DISTRIBUTION. Brazil (S Bahia, Espirito Santo?, Rio de Janeiro, Sao Paulo): epiphytic and epilithic in perhumid Atlantic forest, near sea level to c.1300 m altitude.

This taxon has the thinnest stem-segments amongst the Brazilian species and is very closely related to R. crispata, but appears to be rare in cultivation, where it needs some shade and high humidity to succeed. As to type, R. crispimarginata Lofgren (1918) is a synonym of R. oblonga, as has been confirmed by field studies at the type locality they share, but in cultivation this name is commonly misapplied to R. crispata (Haworth) Pfeiffer.

R. oblonga is also very similar to R. goebeliana from Bolivia and to R. occidentalis from northern Peru, southern Ecuador and Suriname. They differ from R. oblonga in their stem-segments being consistently narrowly cuneate at base, the pericarpel of R. goebeliana being more elongate and the flowers of R. occidentalis generally smaller than those of the Brazilian species.

A red-fruited variant or ally of R. oblonga, from the Serra dos Orgaos (RJ), with somewhat smaller but thicker stem-segments, is of uncertain taxonomic position and merits further study. It is sometimes encountered in cultivation under the inadequately typified name, R. rhombea (Salm-Dyck) Pfeiffer.

Top left photo: copyright Derek Butcher, top right photo: copyright Luc Scherens.