Orchids of New Guinea

Next Genus: Genus Thelasis section Hemithelasis

Genus Thelasis

Thelasis Blume, Bijdr. (1825) 385

Synonyms:

Genus Euproboscis Griff., Calcutta J. Nat. Hist. 5 (1845) 371
Genus Oxyanthera Brongn. in Duperrey, Voy. Coq. Bot. (1829) 197
Genus Rhynchophreatia Schltr., Bot. Jahrb. Syst. 56 (1921) 488

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 leaves arranged in two rows. 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 fleshy, 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 or very short. Pollinia 8, solid, caudicles present, stipe absent, viscidium present.

Distribution:

Southeast Asia, Indochina, Malaysia, Indonesia, the Philippines, Papua New Guinea, Australia, Solomon Islands. About 25 species; in New Guinea about 15 species.

Habitat:

Epiphytes in lowland and hill forest.

References:

Pridgeon, A. M., P.J. Cribb, M.W. Chase & F.N. Rasmussen (Eds.). 2005. Genera Orchidacearum, Volume 4: Epidendroideae (Part one). Pp. 593-596. Oxford University Press, Oxford.

Classification:

Subfamily Epidendroideae
Tribe Podochileae
Subtribe Thelasiinae
Genus Thelasis

Notes:

Genus Thelasis in New Guinea contains 15 species:

Thelasis abbreviata
Thelasis angustifolia
Thelasis carinata
Thelasis compacta
Thelasis copelandii
Thelasis cycloglossa
Thelasis edelfeldtii
Thelasis gautierensis
Thelasis globiceps
Thelasis mamberamensis
Thelasis micrantha
Thelasis phreatioides
Thelasis pygmaea
Thelasis sphaerocarpa
Thelasis wariana

KEY TO THE SECTIONS OF THE GENUS THELASIS

1a Plant with distinct, 1- or few-leaved-pseudobulbs == section Thelasis
1b Plant without distinct pseudobulbs ... 2

2a Column-foot absent == section Oxyanthera
2b Column-foot present == section Hemithelasis

Thelasis is undoubtedly one of the least ornamental of all orchid genera. It is very closely related to Phreatia and rarely seen in cultivation, except in scientific collections. These are small to medium size epiphytes with fleshy, green or whitish flowers that do not open widely. As in Phreatia, some species have distinct pseudobulbs while in others these are lacking. Delimitation against the related genus Phreatia is complicated by the existence of a group of intermediate-looking species, which Schlechter, after including them in Phreatia, decided to put in a genus of their own. This genus, called Rhynchophreatia, was taken up in the checklist on the CD Orchids of New Guinea vol. 1, but after having studied living specimens we agree with J.J. Smith, who included this group of species as a section Hemithelasis in the present genus. These species differ from Thelasis in the strict sense by the possession of a short but distinct column-foot; on the other hand, the very fleshy flowers and the long rostellum (except in the especially problematic Thelasis sphaerocarpa) place them in Thelasis. The final word on this issue has yet to be spoken.