Erect to pendulous epiphytes or lithophytes with coarse roots and relatively thick fibrous leafy stems, the relatively large, crowded, thick, leathery leaves arranged in 2 ranks. Inflorescences are either simple and unbranched or branched and the flowers usually face towards the apex. They have thick-textured segments and a stiffly attached deeply pouched labellum with a narrow internal structure that extends forwards from the rear wall. The column is short and lacks a column foot.
Significant Generic Characters
Epiphytic/lithophytic orchids; plants small to large, erect to pendulous; stems fibrous; leaves crowded, in 2 ranks, much longer than wide, leathery, unequally notched; flowers relatively small, lasting several days; perianth segments thick-textured; sepals subsimilar; petals slightly smaller than the sepals; labellum firmly attached to the base of the column; lamina 3-lobed, with a deeply pouched basal spur; bases of lateral lobes fused to basal margins of the column; spur containing a single narrow callus structure attached to the posterior margin and extending diagonally from the posterior wall to the top of the anterior wall, occasionally this callus structure fused to the lateral walls of the spur; column short, lacking a foot; pollinia 4, sessile on a stipe, in 2 unequal pairs.
Size and Distribution
A genus of about 30 species distributed in South-east Asia, Malesia, Melanesia, including New Guinea, and some islands of the Pacific. Two species, Pomatocalpa macphersonii and P. marsupiale, occur in northeastern Queensland, neither endemic. Pomatocalpa macphersonii is widely distributed between Cape York (10º41' S) and Rockhampton (23º22' S), whereas P. marsupiale is restricted to the Iron Range and McIlwraith Range on Cape York Peninsula. State occurrence: Queensland.
Ecology
Pomatocalpa macphersonii grows on trees in rainforest at low to moderate altitudes. Pomatocalpa marsupiale mainly grows on the upper branches of trees near streams but has also been found occasionally on boulders and cliff faces, also at low to moderate altitudes. The climate is tropical and the majority of rain falls during the summer wet season (December to March), with the remaining months much drier and having sporadic or intermittent rain.
Biology
Pollination: The flowers of Pomatocalpa species last many days and are pollinated by native bees.
Reproduction: Reproduction in Pomatocalpa is solely from seed. Seed dispersal takes 10-12 months after pollination and the capsules develop in a pendulous position. Apomixis is unknown in the genus.
Seasonal Growth: Plants of Pomatocalpa species grow mainly during the spring and summer months and are relatively quiescent for the remainder of the year.
Flowering: Pomatocalpa macphersonii flowers between July and October; Pomatocalpa marsupiale flowers at intervals throughout the year.
Hybrids: Natural hybrids involving species of Pomatocalpa are unknown in Australia.
Derivation
Pomatocalpa, which is derived from the Greek pomatos, drinking cup and calpe, pitcher, refers to the deeply pouched labellum.
Botanical Description
Perennial, evergreen, epiphytic or lithophytic herbs (rarely terrestrial), monopodial. Roots thick, elongate, mainly adherent. Plants small to large, erect, porrect or pendulous. Stem relatively thick, short to long, fibrous, sparsely branched. Pseudobulbs absent. Trichomes absent. Leaves lasting several seasons, distichous, sessile, much longer than wide, flat or channelled, thick, coriaceous, smooth; base sheathing the stem, usually imbricate with its neighbour, persistent after leaf abscission; margins entire; apex unequally emarginate. Inflorescence lateral, spicate or paniculate, erect, arcuate or pendulous, arising from a distal axil, multiflowered. Peduncle shorter or longer than the rhachis, with scattered imbricate scarious bracts. Rhachis straight. Floral bracts scarious, sheathing the base of the ovary or pedicel. Pedicel (if present) short, thin, merging with the ovary. Ovary short, mostly straight. Flowers resupinate, relatively small, facing the apex of the inflorescence, stalked or sessile, opening sequentially, lasting many days, brownish, white, cream, reddish or yellow, often with colour patterns. Perianth segments thick-textured, incurved or spreading. Dorsal sepal free, subsimilar to the lateral sepals. Lateral sepals free, subsimilar to the dorsal sepal, flanking the labellum. Petals free, slightly shorter than the sepals. Labellum stiffly attached to the base of the column, the basal margins of the lateral lobes fused to the lower margins of the column, markedly dissimilar in size and shape to the sepals and petals, calcarate. Labellum lamina fleshy, with a basal spur, 3-lobed; spur deeply saccate, widening distally, with a narrow simple or toothed callus structure extending diagonally from the posterior wall of the pouch to the top of the anterior wall, occasionally this callus structure fused to the lateral walls of the pouch, the apex of the anterior wall of the pouch thick and fleshy; lateral lobes fused to the lower margins of the column; mid-lobe short, porrect to recurved, thick, fleshy. Spur (see labellum). Callus (see labellum). Nectar unknown. Column short, porrect from the apex of the ovary, lacking free filament and style, fleshy, nearly straight. Column wings present, lateral. Column foot absent. Pseudospur absent. Anther terminal, incumbent, 2-celled, persistent, smooth, with a narrow curved or hooked rostrum. Pollinarium present. Pollinia 4 in 2 appressed pairs, unequal, orange, hard, waxy, sessile. Stipe well-developed, narrow with revolute margins. Viscidium present, small. Rostellum ventral, bifid. Stigma entire, concave. Capsules dehiscent, glabrous, porrect; peduncle not elongated in fruit; pedicel not elongated in fruit. Seeds numerous, light coloured, winged.
Taxonomy
Within the Vandeae, Pomatocalpa is distinguished by the 3-lobed, deeply pouched labellum, the bases of the labellum lateral lobes fused to basal margins of the column, the labellum spur containing a single narrow callus structure attached to the posterior margin and extending diagonally from the posterior wall to the top of the anterior wall, occasionally this callus structure fused to the lateral walls of the spur, column short, lacking a foot and, 4 sessile pollinia in 2 unequal pairs.
Nomenclature
Pomatocalpa Breda, Kuhl & Hasselt in Breda, Gen. sp. Orchid. Ascelp. (29), t.[15] (1829).
Type species: Pomatocalpa spicatum Breda.
Infrageneric Taxa: No infrageneric taxa are currently recognised.
References
Dockrill, A.W. (1967). Australasian Sarcanthinae. The Australasian Native Orchid Society, Sydney.
Dockrill, A.W. (1969). Australian Indigenous Orchids. Volume 1. The Society for Growing Australian Plants, Halstead Press, Sydney.
Dockrill, A.W. (1992). Australian Indigenous Orchids. Volume 1 & 2. Surrey Beatty & Sons in association with The Society for Growing Australian Plants, Chipping Norton, NSW.