Monographs Details: Tolumnia
Authority: Ackerman, James D. 1995. An orchid flora of Puerto Rico and the Virgin Islands. Mem. New York Bot. Gard. 73: 1-203.
Description:Distribution and Ecology - Plants sympodial, mostly small twig epiphytes, rarely lithophytic or terrestrial. Roots velamentous. Rhizomes short or wiry. Stems minute, usually hidden by leaf bases, sometimes pseudobulbous. Leaves articulate, arranged fanlike, fleshy-coriaceous, conduplicate, laterally compressed or subterete, psygmoid (incorrectly referred to as "equitant"). Inflorescences lateral from between leaf bases, pedunculate, racemose or paniculate, few- to many-flowered. Flowers generally colorful, showy, resupinate. Dorsal sepal free, erect; lateral sepals free or connate. Petals free, spreading, usually larger than the dorsal sepal. Lip attached to the base of the column, nectary absent, trilobed, middle lobe usually emarginate; disc callus tuberculate, glabrous to pubescent. Column erect, semiterete, stigma flanked by lateral wings, footless; tabula infrastigmatica present; anther terminal, operculate, incumbent; pollinia 2, hard, waxy, stipe elongate, attached to a small viscidium. Fruit a capsule. Chromosomes: 2n = 40, 42, 84, 133 (Moir & Moir, 1980).
Discussion:Tolumnia Rafinesque, Fl. Tellur. 2: 101, No. 382, 383. 1837 . Type species. Tolumnia pulchella (Hooker Rafinesque, based on Oncidium puchellum Hooker f. of Jamaica.
A genus of about 30 species, some not well defined. Most species occur in the Greater Antilles, but some are known from southern Florida (U.S.A.), the Bahamas, and the Lesser Antilles.
Popularly known as the "variegata" or "equitant" group of oncidiums, Tolumnia is vegetatively distinct from Oncidium. Furthermore, chromosome numbers and recent cpDNA data support the segregation of Tolumnia from Oncidium (Chase 1986c; Chase & Palmer, 1992).
Special Literature. Garay, 1970; Garay & Stacy, 1974; Moir & Moir, 1980; Withner, 1980; Dressier & Williams, 1982; Braem & Liickel, 1983; Braem, 1986; Chase, 1986c; Chase & Palmer, 1992