Monographs Details: Rogersonanthus arboreus (Britton) Maguire & B.M.Boom
Authority: Maguire, Bassett. 1989. The Botany of the Guayana Highland- Part XIII. Mem. New York Bot. Gard. XIII: 1-127.

Type. Trinidad. Virgate tree 5 m, corolla green-yellow, forest bank nr. the summit, Mt. Tocuche (Blanchisseuse Rd., top of M o m e Bleu), 3-5 Apr 1920, N. L. Britton, T. E. Hazen & W. Mendelson 1295 (holotype N Y ).

Chelonanthus arboreus Britton, Bull. Dept. Agric. Trin. &Tob. 19:230. 1922

Macrocarpaea arborea (Britton) Ewan, Contr. U.S. Natl. Herb. 29:221. 1948.

Rogersonanthus arboreus, the extra-Guayanan but closely related member of this assemblage, originally described under Chelonanthus, is historically the second species ofthe present alliance to have been discovered. Britton recognized its close generic affinity more accurately than did later students.

This Trinidadian element is known to us only by Britton's type and a fragment oi^'Trin Herb 10128,'' collected by Williams at the type locality in 1922. From this meager representation very little can be learned about the population as it obtains on Mt. Touche. Negligible distinction of the specimen from the considerably disjunct Rogersonanthus tepuiensis, as recognized by Ewan (1948), is allowed here chiefly on historic and geographic grounds. Maas (1985) placed Chelonanthus arboreus in synonymy with Irlbachia quelchii.