Thelasis Blume,
Bijdr. (1825) 385
Sympodial epiphytes with very short to rather long rhizomes. Pseudobulbs present or not, consisting of one to several internodes, 1- to few-leaved; when pseudobulbs absent stem short, few- to many-leaved, with the distichous leaves. Leaves sheathing or not, glabrous, deciduous, duplicate, leathery. Inflorescence arising from the base of the pseudobulb, or lateral from the stem, a many-flowered raceme. Flowers very small, resupinate, often hardly opening, white or green, soon becoming yellowish. Sepals free or connate at the base. Petals free, usually about as long as the dorsal sepal but mostly dissimilar to it. Lip without spur, not mobile. Column-foot absent. Pollinia 8, solid, caudicles present, stipe absent, viscidium present.
Distribution
Southeast Asia, Indochina, Malaysia, Indonesia, the Philippines, Papua New Guinea, Australia, Solomon Islands; about 20 species.
Distribution in the Philippines
Camiguin de Babuyanes, Luzon (Kalinga-Apayao, Cagayan, Bataan, Rizal, Laguna, Quezon, Tayabas, Albay, Sorsogon), Polillo, Mindoro, Palawan, Panay, Negros, Leyte, Samar, Mindanao (Zamboanga, Bukidnon, Surigao, Agusan, Davao, Cotabato), Basilan, Sulu; 5 species.
Habitat
Epiphytes in lowland and hill forest.
Notes
Thelasis is one of the least ornamental of all orchid genera, with tiny whitish or green flowers that hardly open. It is very closely related to Phreatia and is rarely seen in cultivation, except in scientific collections.