Monographs Details: Roentgenia
Authority: Maguire, Bassett. 1978. The botany of the Guayana Highland--part X. Mem. New York Bot. Gard. 29: 1-288.
Discussion:20. Roentgenia Urban, Ber. Deutsch. Bot. Ges. 34: 747. 1916.
Type. R. bracteomana (K. Schum. ex Sprague) Urb.
A bitypic genus, Roentgenia is barely separable from Cydista. It differs chiefly in trifid rather than simple tendrils. The "Cydista-type" flowers are usually white with purple markings, and lack a nectariferous disc. The corolla is lepidote outside, the calyx cupular, the inflorescence usually axillary and the fruit linear. Roentgenia has terete branchlets and lacks pseudostipules and interpetiolar glandular fields when mature. One species occurs from Peru to Colombia, the other in the Guayana lowlands.