Tolumnia Raf.

George R. Proctor (2012). Flora of the Cayman Isands (Second Edition). Royal Botanic Gardens, Kew

Morphology General Habit

Mostly small twig epiphytes, rarely lithophytic or terrestrial, with short or long and wiry rhizomes

Morphology Stem

Stems small, usually completely hidden by leaf bases, sometimes pseudobulbous

Morphology Leaves

Leaves articulate, fan-like arrangement, fleshy coriaceous, conduplicate, laterally compressed or subterete, psygmoid (incorrectly referred to as “equitant”)

Morphology Reproductive morphology Inflorescences

Inflorescences lateral from between leaf bases, pedunculate, racemose or paniculate, few–many-flowered

Morphology Reproductive morphology Flowers

Flowers generally colorful, showy, resupinate; dorsal sepal free, erect, lateral sepals free or variously connate; petals free, spreading, usually larger than the dorsal sepal; lip attached to the base of the column, nectary absent, trilobed, midlobe usually emarginate, disc callus absent to tuberculate, glabrous to pubescent

Morphology Reproductive morphology Flowers Column

Column erect, semiterete, footless, subapical lateral wings flanking the stigma footless, tabula infrastigmatica present

Morphology Reproductive morphology Flowers Androecium Stamens Anthers

Anther terminal, operculate, incumbent, pollinia 2, hard, waxy, attached to an elongate stipe with a small viscidium

Morphology Reproductive morphology Fruits

Capsules ellipsoidal.

Distribution

A genus of 25 species, some not well-defined. Most species occur in the Greater Antilles, but some are known from the United States (southern Florida), the Bahamas and the Lesser Antilles.

Recognition

Popularly known as the “variegata” or “equitant” group of oncidiums, Tolumnia is vegetatively distinct from Oncidium but the flowers are very similar, probably owing to evolutionary convergence. Vegetative morphology, chromosome numbers and molecular sequence data are all congruent and support the segregation of Tolumnia from Oncidium.