AFRICAN

ORCHIDS

Orestias Ridl.., J. Linn. Soc, Bot. 24: 197 (1887).
Synonyms:
Kornasia Szlach., Fragm. Florist. Geobot., Suppl. 3: 120 (1995).
Lisowskia Szlach., Fragm. Florist. Geobot., Suppl. 3: 121 (1995).
Description:
Plants rather small, uniform in habit, few too many gathered in compact clusters. Rhizome between shoots very short. Leafy stem erect, slender, mostly covered by leaf petioles, sheaths and basal scales. Basal scales infundibular, free part attenuate and acute, paler. Leaves 2 - 4 ; leaf petiole abbreviated; leaf sheath infundibular, loose; leaf blade slightly oblique, broadly ovate, ovate to oblong ovate, older broader, attenuate, (3 -) 5-nerved. Inflorescence erect, terminal; raceme with 20 - 100 flowers, cylindrical, dense, delicate. Sterile bracts several, lanceolate, 1-nerved, deflected. Floral bracts lanceolate, attenuate, acuminate at apex, 1-nerved, deflected. Flowers resupinate, small, often variable in colour, from pale greenish, yellowish to dark red, purple-red, brownish red, with characteristic intense and dark coloured spot at the middle of lip lamina. Sepals 3-nerved, sometimes with 2 quickly vanishing lateral nerves. Dorsal sepal apiculate at apex, slightly cordate at base. Lateral sepals falcate, ovate, apiculate at apex,cordate and connate at base. Petals distinctly falcate, lanceolate, tapering at upper portion, apiculate at apex, broader at basal portion, cordate at base, 1-nerved, often with an additional, lateral, shorter nerve. Lip with well developed obliquely positioned basal auricles, almost rectangular, thick, with raphide cells; lip lamina with characteristic pubescent cushion(s) in the middle portion of lip lamina, 3 main subparallel nerves, vanishing distinctly before distal margins, external ones with two branches at basal part. Gynostemium (most important distinguishing features for the genus and unique amongst other representatives of the subtribe): column elongate, slender, cylindrical, erect when young, turning to the lip with age, gradually tapering towards the rostellum base; rostellum very large, oblong, triangular to flabellate, distinctly erumpent out of lateral margins of anther, widely spread; throat of stigma pocket only partly overlapping base of the rostellum, just below of it; stigma pocket reaching deeply inside the column; anther only slightly different in shape, firmly attached to the column apex by distinct filament, pale yellow to cream, but always with locules opening laterally, locules large, shallow, usually erumpent out of anther margins; pollinia 4, binate, large, oblong, curved, only at small basal portion hidden in locules, lying transversally, narrower tip gently connate with distal part of rostellum, bright yellow. Fruit oblong obovate, yellowish to fawn.
Distribution:
WC. Trop. Africa
Cultivation:
Not in cultivation
Species:

Orestias elegans Ridl. São Tomé, Príncipe.
Orestias foliosa Summerh. WC. Trop. Africa.
Orestias micrantha Summerh. São Tomé, Cameroon to Equatorial Guinea.
Orestias stelidostachya (Rchb.f.) Summerh. São Tomé.

World Checklist of Monocotyledons. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the Internet; http://www.kew.org/wcsp/monocots/ accessed1/20/2010
Bibliography and References:
Margonska HB, Szlachetko DL. 2005 Taxonomic revision of the African genus Orestias Ridl. (Malaxidinae, Orchidaceae). Ann. Naturhist. Mus. Wien, 107B. 209-220
Summerhayes V.S. 1937. Orestias stelidostachya. Bull. Misc. Inf. Kew, 460.