Mediocalcar umboiense Schuit., Orchid Monogr. 8 (1997) 63, fig. 22
Type: Edinburgh cult. (Argent s.n.) 721246 (holo E, spirit material; iso L, spirit material)
Roots densely covered with root hairs, 0.5-0.8 mm thick. Rhizome creeping, freely branching, mat-forming, 2 mm thick. Cataphylls 3-5, subacute, keeled. Pseudobulbs prostrate, 3-17 mm apart, cylindrical to slightly clavate, glabrous, 7-20 mm long, 4-6 mm across; almost entirely adnate to the rhizome. Leaves three or four, occasionally two, per pseudobulb, very shortly petiolate, spreading in one plane, narrowly elliptic (index 3.5-6.3) 2-3.5 cm by (4-)5-10 mm; broadly sulcate along the midvein; apex obtuse, bilobulate, mucronate, with the mucro about as long as the lobules; carnose. Inflorescences solitary, heteranthous or infrequently synanthous, at the base with a rudimentary scale. Peduncle 5-7 mm long, at the apex with a triangular, acuminate bract 1.5 mm long. Pedicel and ovary c. 6.5 mm long. Flowers urceolate-globose, oblique, 7.5-8 mm long. Synsepalum c. 12 mm long and c. 16 mm wide when cut open and flattened; free tips patent, narrowly triangular, 4.5 mm long, acute; sepals conspicuously gibbose. Petals linear (index c. 8), c. 7.2 by 0.9 mm; apex subacute, 1-nerved. Lip c. 7.6 by 5 mm in natural position, the blade broadly ovate when flattened; claw c. 1.1 by 2.3 mm, auricles inconspicuous; apex acute, reflexed; margins erect, clasping the column; spur saccate, recurved, parallel to the column, c. 1.6 mm long, c. 3 mm wide just below the mouth. Column broadly clavate, c. 3.1 mm long, 2.2 mm wide at the apex; foot very short. Fruit not seen. (After Schuiteman, 1997)
Colours: Flowers bright orange with yellow tips to the sepals, petals and lip. Enclosed parts of petals and lip pale orange. Column cream colour. Pollinia white. Leaves mid green above, pale green below. Pseudobulbs pale green.
Habitat: Epiphyte in lower montane forest; 600 m.
Flowering time in the wild: December.
Distribution: Malesia (New Guinea, endemic).
Distribution in New Guinea: Papua New Guinea. See map: 436-64M.JPG.
Cultivation: Intermediate growing epiphyte.
Notes: Very similar to Mediocalcar decoratum, but consistently larger in its vegetative parts and with narrower free segments to the sepals. Mediocalcar umboiense is only known from the eponymous island on which it was discovered by George Argent from the Royal Botanic Garden Edinburgh.