Orchids of New Guinea

Genus Cleisostoma

Cleisostoma Blume, Bijdr. (1825) 362

Synonyms:

Genus Blumeorchis Szlach., Ann. Bot. Fennici 40 (2003) 68
Genus Carteretia Rich., Sert. Astrol. (1834) 10. t. 4
Genus Echioglossum Blume, Bijdr. (1825) 364
Genus Garayanthus Szlach., Fragm. Flor. Geobot. Supp. 3 (1995) 136
Genus Ormerodia Szlach., Ann. Bot. Fennici 40 (2003) 68
Genus Raciborskanthos Szlach., Fragm. Flor. Geobot. Supp. 3 (1995) 135
Genus Sarcanthus Lindl., Collect. Bot. (1826) t. 39B (non Lindl. 1824)

Monopodial epiphytes. Stem short or elongated. Leaves few to many, arranged in two rows, sheathing at the base, glabrous, dorso-ventrally flattened or terete (not in New Guinea), deciduous, duplicate, leathery. Inflorescence lateral, a few- to many-flowered raceme or a panicle. Flowers small, resupinate. Sepals free. Petals free, usually somewhat shorter and narrower than the dorsal sepal. Lip rigidly adnate to the column, spurred, spur inside with a longitudinal dividing membrane; the back wall of the spur near the entrance provided with a large callus. Column-foot usually absent. Pollinia 4, equal or unequal, arranged in 2 or 4 bodies, solid, caudicles absent, stipe present, viscidium present.

Distribution:

Tropical continental Asia, Malaysia, Indonesia, the Philippines, Papua New Guinea, Pacific islands, east to Fiji (not in Australia). About 90 species; in New Guinea c. 7 species.

Habitat:

Epiphytic in lowland and montane forest, at high altitudes also terrestrial.

Classification:

Subfamily Epidendroideae
Tribe Vandeae
Subtribe Aeridinae
Genus Cleisostoma

Literature:

Christenson, E.A. 1982. Sarcanthine genera - 1: The genus Cleisostoma Blume. Amer. Orchid. Soc. Bull. 51: 609-614.
Schuiteman, A. & E. F. de Vogel. 2004. Cleisostoma buruense, a first record from New Guinea with a key to the species of Cleisostoma in New Guinea. Journal für den Orchideenfreund 11: 161-171.
Seidenfaden, G. 1975. Orchid genera in Thailand: 2. Cleisostoma Bl. Dansk Bot. Ark. 29(3): 1-80.
Ormerod, P. 2008. Notes on the Cleisostoma gjellerupii (J.J.Sm.) Garay complex in New Guinea. Orchadian 16: 82-87, fig.

Notes:

A genus of small-flowered monopodial orchids, related to Micropera, Pomatocalpa, Malleola, etc., from which it is distinguished by the large callus inside the mouth of the spur that almost blocks entrance. Cleisostoma is the largest genus in this alliance. Due to its rather inconspicuous flowers it is of limited horticultural value.

The genus Cleisostoma in New Guinea contains 10 species:

Cleisostoma buruense
Cleisostoma clemensiae
Cleisostoma firmulum
Cleisostoma gjellerupii
Cleisostoma isuaravanum
Cleisostoma litoreum
Cleisostoma micholitzii
Cleisostoma paludosum
Cleisostoma platystele
Cleisostoma stimulatrix

Key to Species of the The Cleisostoma gjelierupii complex (New Guinean Cleisostoma species which have greenish sepals and petals that are blotched with brown (not striped or unmarked) and a labellum midlobe with a basal median triangular callus).

1a. Lip lacking a small lobule at the junction of the outer margins of the midlobe and sidelobes. == Cleisostoma clemensiae Ormerod

1b. Lip with a small lobule at the junction of the outer margins of the midlobe and sidelobes. == 2

2a. Leaves ovate-elliptic. Lip midlobe with a forward-pointing, obtuse medial callus == Cleisostoma paludosum (van Royen) T.M. Reeve

2b. Leaves ligulate to oblong-ligulate. Lip Midlobe of the lip with an upward-pointing, acute medial callus == 3

3a. Lateral sepals obliquely elliptic, 3.4 mm wide. Lip sidelobes rectangular == Cleisostoma isuaravanum Ormerod

3b. Lateral sepals obliquely oblong, 2.5 mm wide. Lip sidelobes triangular == Cleisostoma gjellerupii (J.J.Sm.) Garay

(after Ormerod 2008)