Didymochlamys Hook.f. includes two species of small, usually epiphytic herbs found in northern South America and southern Central America. These plants grow on boulders and tree trunks in wet forests, and are often overlooked as Rubiaceae. Their leaves are distichous and opposite but strongly anisophyllous, and may appear alternate if not examined carefully. The interpetiolar stipules of Didymochlamys are quite small and quickly caducous, so that the smaller leaf of the anisophyllous pair may be mistaken for a stipule, and Didymochlamys is therefore sometimes confused with Gesneriaceae.

The inflorescences of Didymochlamys are distinctive, with a short fascicle of 2-5 flowers enclosed in two enlarged green bracts that are held pressed flat together; the genus name refers to these bracts. The relatively small flowers are white to blue or violet, and their lobes have the margins crisped to incised or appendaged. The cupuliform fruits are berrylike at least in their early stages, although those of Didymochlamys connellii are reportedly later dehiscent though at the apex. The numerous seeds are small and bear a tuft of silky trichomes at one end, similarly to the seeds of Hillia Jacq.

The relationships of Didymochlamys within the Rubiaceae are not yet clear, and this genus has never been studied in any detail. It has generally been associated with genera now included in Cinchonoideae, but it has raphides in its tissues; these are found throughout the genera of Rubioideae, but only in a few genera of Cinchoneae. The Cinchonideae tribe that is notable for its raphides is Hillieae, which includes a number of epiphytes. The unusual seed form of Didymochlamys is only otherwise found in Hillia, and it may have its relationships in this tribe.

Steyermark (1967: pp. 290-291) did review this genus but only briefly. Steyermark (1974) presented a floristic treatment for Didymochlamys connellii in Venezuela and an illustration (1974: p. 428, fig. 70). Dwyer (1980) presented a floristic treatment of Didymochlamys whitei in Panama and an illustration (1980: p. 148, fig. 33), but incorrectly called the Panamanian plants "Didymochlamys connellii".

Author: C.M. Taylor
The content of this web page was last revised on 18 May 2020.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

Neotropics: in wet lowland forests at 100-1100 m, one species in southern Nicaragua through northwestern Ecuador and the other in southern Venezuela to Guyana.

• Steyermark, J. A. 1967. Rubiaceae. In: B. Maguire & collaborators, The botany of the Guayana Highland—Part VII. Mem. New York Bot. Gard. 17(1): 230–439.
• Steyermark, J. A. 1974. Rubiaceae. 9(1–3): 7–2070. In T. Lasser (ed.) Fl. Venezuela. Fondo Editorial Acta Científica Venezolana, Caracas.
• Dwyer, J.D. 1980. Flora of Panama, part IX. Family 179. Rubiaceae - part 1. Ann. Missouri Bot. Gard. 67(1): 1–256.