69. Tolumnia Rafinesque, Fl. Tellur. 2: 101. 1837.
[Probably for Tolumnius, a Rutulian mentioned by Virgil]
Mark W. Chase & James D. Ackerman
Herbs, epiphytic or rarely terrestrial, ± climbing, fan-shaped. Rhizomes often elongate, covered with bracts; pseudobulbs reduced to absent. Leaves: basal 3–7, apical not more than 1; blade recurved, lanceolate, laterally flattened–3-gonal, margins often serrulate. Inflorescences racemes or weakly paniculate; bracts narrowly triangular. Flowers: sepals and petals spatulate-clawed; lateral sepals sometimes partially connate; lip 3-lobed, pandurate, without nectar cavity; callus prominent tuberculate-lobulate; column with pair of outstretched apical wings, without hood; stigmatic cavity round; rostellum not prominent. Fruits capsules, ellipsoid.
Species 30 (1 in the flora): restricted to s Florida, West Indies.
Tolumnia does not belong to the main body of Oncidium (its traditional placement) even though many of the species have floral morphologies nearly identical to that of Oncidium. It shares, with other twig epiphytes, a fan-shaped habit and seeds with prominent extensions of the testa.
Braem, G. J. 1986. Tolumnia—Der neue, aber doch alte, Name für die “Variegaten Oncidien.” Orchidee (Hamburg) 37: 55–59. Chase, M. W. and J. S. Pippen. 1988. Seed morphology in the Oncidiinae and related subtribes (Orchidaceae). Syst. Bot. 13: 313–323. Williams, N. H., M. W. Chase, T. Fulcher, and W. M. Whitten. 2001. Molecular systematics of the Oncidiinae based on evidence from four DNA sequence regions: Expanded circumscriptions of Cyrtochilum, Erycina, Otoglossum, and Trichocentrum and a new genus (Orchidaceae). Lindleyana 16: 113–139.