AFRICAN

ORCHIDS

Microcoelia macrantha (H.Perrier) Summerh., Bot. Mus. Leafl. 11: 155 (1943).
Homotypic Synonyms:
Gussonea macrantha H.Perrier, Notul. Syst. (Paris) 7: 29 (1938).
Description:
Stem sometimes proliferous, terete, up to 25x2-3 mm. Scale-leaves acute, with 3^4 nerves, up to 3.0 mm long. Roots few to many, usually forming a dense ± conical mass around the stem or ± loosely spreading when older, distal ends distinctly twisted and ± branched, often slightly swollen at the nodes, ± terete, smooth, up to 50 cm long, 1.0-2.0 mm in diameter. Inflorescence(s) ± erect, spreading, up to 4(-7) cm long, up to 5(-8) simultaneously, usually sparse, each with up to 8(—13) flowers; penduncle short, up to 5—10(—20) mm long; rachis ± straight to slightly flexuose, ± terete, smooth (light hellebore green to dark citrine); bracts sheathing, subacute to ± mucronate, basal indistinctly 3-nerved, apical 1-nerved, up to 2.0 mm long, in early stage ± transparent turning into (chestnut-brown) when mature. Pedicel long, terete, slightly furrowed, up to 11 mm long, whitish, at the very base tinged with the colour of rachis; ovary ± straight, slightly furrowed, 2.8-3.9x0.4-1.0 mm, whitish. Flowers ± horizontally orientated, up to 13 mm long excluding pedicel; perianth pure white; spur pure white, except at the light green base and spur mouth; anther light greenish-yellow as androclinium, the rest of the column pure white. Glandular hairs sparsely present on rachis, pedicel, slightly more on the ovary and at the base of the perianth and very sparse at the base of the spur. Dorsal sepal ± convex, oblong to ± obovate, subacute, 3-nerved, central nerve slightly thickened, (4.8-) 6.3—7.7(—9.0) x (1.9-) 2.3-3.0(-4.4) mm. Lateral sepals slightly asymmteric, ± convex, subacute to acute, 3-nerved, central nerve distinctly thickened, (4.2-)4.8-7.2(-9.2) x 2.0-3.0 (-4.7) mm. Petals indistinctly asymmetric, ± convex, obovate to elliptic, obtuse to subacute, 3-5 nerved, lateral nerves branched or not, (3.9-) 6.0-8.4 (-9.0) x (2.3-) 3.2-5.4 mm. Labellum 3-lobed; mid-lobe ± cup-shaped and folded, broadly obovate, emarginate, ± erose, c. 8-nerved, lateral nerves branched; side-lobes rounded, cup-shaped, with a ± distinct thickening at each side of spur mouth, (4.1—)6.3—9.3 (-10.3) x (3.6-) 5.0-11.6 mm when outspread, pure white except for a semicircular band around the frontal spur mouth, (dull green-yellow to apple green); spur large, slightly incurved, flattened from the sides, angular in TS; apex distinctly incurved and inflated, in side view ± triangular in outline with flattened facets, 5.6-8.7 mm long, (1.6-) 1.9-2.7 mm in diameter. Column long, straight, basal part with distinct side lobes, tapering apically, (3.0-)3.4-6.2 (-6.5) mm long, (0.7—) 1.0—1.3(—1.9) mm high, pure white; andro-clinium shallowly excavated with a central ridge, (apple green); rostellujn lobes long, descending, inserted at the base of the androclinium, obtuse, apical margin incurved, up to 1.9 mm long. Anther hemispherical, tapering into an oblong, subacute apex, reflexed or not, 1.7-2.6 x 1.3-1.8 mm, (dull green-yellow) with a triangular patch near the filament (apple green), the apical margin ± transparent. Pollinia subglobose, asymmetric, surface uneven, with ± distinct flattened areas; in side view ± orbicular, 560-700 (-800) x (470-)560-660 µm; in median section ± ellipsoid, proximally ± excavated, distally ± convex, 440-560 µm thick (massicot yellow to straw yellow). Stipes distinctly sigmoid; apical part shallowly channeled, rounded; basal part ± flat, connate with the apical part of the viscidium, (0.8—) 1.0-1.4 x 0.4-0.5 mm (in natural position), transparent; viscidium ± oblong, gradually widened towards the flattened truncate apex, basal part ± convex, notched, 1.4-2.2 x 0.5-0.8 mm, transparent. Capsule short, ellipsoid, c. 9 x3.5 mm (only one empty fruit seen); pedicel short, c. 5 mm long. Scent not percepted.
Habitat:
Rain forest, extending from coastal rain forest to mountain rain forest and occasionally in secondary vegetation, often near water courses, altitude 0-1000 m. Epiphytic in more or less shaded conditions, mostly on smaller branches and twigs, extending almost from the ground up to the crown of the understorey vegetation.
Flowering period:
Mainly at the end of the heavy rainy season (cyclone time).
Notes:
Easily distinguished by the relatively large flowers, the perianth lobes being about 8 mm. long.
Cultivation:
As given for the genus, hot to warm growing epiphyte.
Distribution:
N. & E. Madagascar
References:
Flora Of Madagascar Perrrier 1981; A Monograph of the Genus Microcoelia [Orchidaceae] Jonsson 1981; Angraecoid Orchids Stewart, Hermans, Campbell 2006; Orchids of Madagascar Hermans 2007; Field Guide to the Orchids of Madagascar Cribb & Herman 2009; WCSP (2017). 'World Checklist of Selected Plant Families. 03.03-2017; http://apps.kew.org/wcsp/
Images:
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