AFRICAN

ORCHIDS

Microcoelia megalorrhiza (Rchb.f.) Summerh., Bot. Mus. Leafl. 11: 158 (1943).
Homotypic Synonyms:
Angraecum megalorrhizum Rchb.f., Otia Bot. Hamburg.: 117 (1881).
Angorchis megalorrhiza (Rchb.f.) Kuntze, Revis. Gen. Pl. 2: 651 (1891).
Epidorchis megalorrhiza (Rchb.f.) Kuntze, Revis. Gen. Pl. 2: 660 (1891).
Gussonea megalorrhiza (Rchb.f.) Schltr., Beih. Bot. Centralbl. 36(2): 93 (1918).
Description:
Stem up to 35x3-4.5 mm. Scale-leaves acuminate to rostrate, with 6-7 nerves, up to 6.8 mm long. Roots long, mostly few, variously spreading and twisting, often branched distally, ± loosely attached to the substrate, ± terete, distinctly verrucose, up to 30(—50) cm x 1.5-2.5(3.0) mm, when living having a silvery yellow brown lustre in a ± dry state. Inflorescence(s) ± erect or pendulous, spreading, up to 130 mm long, up to 10 simultaneously, usually ± sparse, each with up to 20 flowers; peduncle short, up to 10 mm long; rachis straight to indistinctly flexuose, ± terete and slightly excavated; bracts sheathing, acute, with 0-3 nerves, 2.0(-2.6) mm long, transparent yellow brown. Pedicel short, ± geniculate, up to 2.0 mm long, fading into salmon pink; ovary straight, 3.0-3.9x0.5-0.7 mm, fading into salmon pink. Flowers ± horizontal, up to 12 mm long including ovary and pedicel, whitish, basal part of the tepals and apical part of the spur fading into salmon pink. Glandular hairs ± dense, scattered on pedicel and ovary, sparsely on rachis, bracts and at the base of the tepals. Dorsal sepal narrowly elliptic to narrowly oblong, acuminate, with a slightly bulging area, 3-nerved, 5.7-7.0 x1.8-2.4 mm. Lateral sepals slightly asymmetric, narrowly oblong, acuminate, 3-nerved, 6.6-8.7 x 1.6—2.4 mm. Petals narrowly elliptic, acuminate, apically ± erose, 5.6-7.4 x 1.8-2.4 mm. Labellum large, 3-lobed; mid-lobe subspathulate, deeply concave, ovate, acuminate, apically ± erose, 5-nerved, lateral nerves with branches; side-lobes narrowly oblong, thickened towards the spur mouth, 6.5-8.1 x 2.2-3.5 mm; spur cylindrical, ± semicircularly curved, tapering into a narrowly conical-shaped obtuse apex, 6.2-7.5x0.7- 1.0 mm, along curve up to c. 10 mm long. Column elongated, slightly recurved, with a central trigonal pillar-like thickening, 1.8-2.7 mm long, 1.0-1.4 mm high; androclinium shallowly excavated, with an indistinct mid-ridge; rostellum lobes long, ± perpendicular, rounded-truncate, up to 1.1 mm long, each up to 0.6 mm wide. Anther ± narrowly triangular in outline; in sideview bivalvate and ± flattened dorsally, tapering into a channelled ± geniculate, narrowly obtuse apex, 2.1-2.7 x c. 1.0 mm. Pollinia asymmetric, 500 – 600 x 500 - 550 µm; in median section ± elliptic, up to 300 µm. Stipes long, indistinctly sigmoid, channelled, with a head-like apex, tapering into a flattened, very narrow base, 1.8-2.6 mm long, 0.5-0.7 mm wide apically; viscidium minute, elliptic to obovate, membranous, 0.3-0.5 x 0.09-0.13 mm. Capsule long, straight, narrowly cylindric to narrowly ellipsoid, distinctly ribbed, 15-24x4-7 mm; pedicel short, up to 3.0 mm long. Seeds fusiform, testa cells narrowly elongate (in a dry state), with ± club-shaped and hook-shaped processes; anticlinal walls ± sulcate with finer striations, or narrowly grooved, terminal ends distinctly elongated, (470-)610-790 (-920) x 35-70 µm (65 dry seeds measured).
Habitat:
Dry woodland, usually on finer branches in the crowns of large trees. Altitude, c. 10-550 m.
Flowering period:
During the late rainy season.
Notes:
Easily distinguished by the verrucose roots. The lip lamina is narrower than in Microcoelia koehleri (Schltr.) Summerh.,the rostellum lobes are more acute and the viseidium is shorter and broader.
Cultivation:
As for the genus, in fairly good light, at intermediate to warm tem peratures. Although this species is rare in the wild, it seems to grow well in cultivation.
Distribution:
Kenya to Malawi
References:
Orchids of Kenya Stewart 1996; A Monograph of the Genus Microcoelia [Orchidaceae] Jonsson 1981; Malawi Orchids La Croix 1983; Flora of Tropical East Africa Orchidaceae Part 3 Cribb 1989; Orchids of Kenya Stewart & Campbell 1996; Flora Zambesiaca Vol 11 Part 2 Pope 1998; AOS Bulletin Vol 71 No 7 2002; AOS Bulletin Vol 72 No 3 2003; Angraecoid Orchids Stewart, Hermans and Campbell 2006; WCSP (2017). 'World Checklist of Selected Plant Families. 03.03-2017; http://apps.kew.org/wcsp/
Images:
Click on each image to see a larger version.