Erect epiphytes or lithophytes with thick roots and long thick fibrous leafy stems. The relatively large, thick, well-spaced leathery leaves are arranged in 2 ranks. Inflorescences are racemes or panicles. The flowers, which last a few days, are dull-coloured and have thick-textured segments. The stiffly attached labellum has a deeply pouched apical spur with a broad concave internal structure that is attached near the apex of the far wall and extends forwards over the opening to the spur. The column is short and lacks a column foot (or has a vestigial one).
Significant Generic Characters
Epiphytic/lithophytic orchids; plants large, erect or climbing; roots thick; stems long, fibrous; leaves well-spaced, arranged in 2 ranks, widely spaced, much longer than wide, thick, leathery, unequally notched; inflorescence racemose or paniculate; flowers opening sequentially; perianth segments thick-textured; sepals subsimilar; bases of the lateral sepals fused to the underside of the labellum; petals slightly smaller than the sepals; labellum firmly attached to the base of the column (? or apex of vestigial column foot); lamina 3-lobed, deeply pouched; spur apical, continuous with the labellum base, deeply saccate, with a broad, apical, inward-facing callus structure attached to the anterior wall and extending across the orifice; column short, lacking a foot (? or with a vestigial foot); pollinia 4, sessile on a stipe, in 2 subequal pairs.
Size and Distribution
A genus of about 12 species distributed in Malaysia, Philippines, Indonesia, New Guinea and Australia where there is a single non-endemic species, Micropera fasciculata. It is widespread between Cape York (about 10º41’ S) and near Townsville (about 19º16’ S) in northeastern Queensland. State occurrence: Queensland.
Ecology
Micropera fasciculata grows on rocks, cliff faces and trees in rainforest at low altitudes, usually in bright light and high humidity. 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 Micropera fasciculata last a few days and are probably pollinated by native bees.
Reproduction: Reproduction in Micropera fasciculata is solely from seed. Seed dispersal takes 10-12 months after pollination and the capsules develop in a porrect position. Apomixis is unknown in the genus.
Seasonal Growth: Plants of Micropera fasciculata species grow mainly during the spring and summer months and are relatively quiescent for the remainder of the year.
Flowering: Micropera fasciculata flowers in autumn-winter.
Hybrids: Natural hybrids involving Micropera fasciculata are unknown.
Derivation
Micropera, which is derived from the Greek micros, small and pera, sac, refers to the labellum spur.
Botanical Description
Perennial, evergreen, epiphytic or lithophytic herbs, monopodial. Roots thick, elongate, mainly adherent. Plants mostly large, sparsely branched from the base, erect or climbing. Stem relatively thick, long, fibrous, leafy throughout. Pseudobulbs absent. Trichomes absent. Leaves lasting several seasons, distichous, sessile, relatively large, usually well-spaced, spreading widely, much longer than wide, flat, thick, coriaceous, smooth; base sheathing the stem, usually imbricate with its neighbour, persistent after leaf abscission; margins entire; apex unequally emarginate. Inflorescence lateral, racemose or paniculate, few to many-flowered. Peduncle longer than or similar to the rhachis, with scattered scarious bracts. Rhachis straight. Floral bracts scarious, sheathing the base of the pedicel. Pedicel short, merging with the ovary. Ovary short, straight. Flowers non-resupinate, well-spaced, relatively small, stalked, opening sequentially, lasting a few days, cream to yellowish. Perianth segments relatively thick-textured, spreading or reflexed. Dorsal sepal free, subsimilar to the lateral sepals. Lateral sepals fused at the base to the proximal underside of the labellum, subsimilar to the dorsal sepal, subtending the labellum. Petals free, slightly shorter than the sepals, often reflexed. Labellum stiffly attached to the base of the column (or apex of the vestigial column foot), at right angles, markedly dissimilar in size and shape to the sepals and petals, calcarate. Labellum lamina fleshy, deeply pouched, with a very thick proximal wall and deep apical spur, 3-lobed; spur deeply saccate, distal from the column and continuous with the base of the labellum, containing a broad concave structure attached near the apex of the distal wall and extending inwards; lateral lobes short, broad, free; mid-lobe very short, fleshy, entire. Spur (see labellum). Callus (see spur). Nectar unknown. Column relatively long, porrect from the apex of the ovary, lacking free filament and style, fleshy, nearly straight. Column wings present, elongate. Column foot vestigial or absent. Pseudospur absent. Anther terminal, incumbent, 2-celled, persistent, smooth, with a long narrow entire rostrum. Pollinarium present. Pollinia 4 in 2 appressed pairs, subequal, orange, hard, waxy, sessile. Stipe well-developed, long, very narrow. Viscidium present, small. Rostellum elongate, narrow. 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, Micropera is distinguished by thick roots, long fibrous erect or climbing stems, well-spaced leathery leaves, racemose or paniculate inflorescence, bases of the lateral sepals fused to the basal underside of the labellum, labellum with a deep apical spur continuous with the labellum base, the spur containing a broad, concave, inward-facing callus structure attached near the top of the distal wall, column short, with a vestigial foot or none and, 4 sessile pollinia in 2 subequal pairs.
Notes
Micropera fasciculata forms large coarse clumps with erect sparsely branched stems. Its flowers open sequentially along the raceme, each flower lasting 5-7 days unless pollinated.
Nomenclature
Micropera Lindl., Edwards’s Bot. Reg. 18: t.1522 (1832). Type species: Micropera pallida (Roxb.) Lindl., Aerides pallida Roxb.
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.