AFRICAN

ORCHIDS

Orestias micrantha Summerh., Bull. Misc. Inform. Kew 1937: 460 (1937).
Description:
Plants (10 -) 15 - 30 cm tall, few to many compactly clustered. Rhizome few mm long between shoots, 1 - 2.4 mm Ø, sometimes branched, node scales loose. Leafy stem (5 -) 8 - 15 cm long, (0.1 -) 0.15 - 0.25 (- 0.3) cm Ø; basal scales 2-3, (0.6 -) 1 - 2.5 cm long, 0.18 - 0.45 cm Ø. Leaves 3-4; leaf petiole (0.15 -) 0.3 - 0.6 (- 0.8) cm long, (0.28 -) 0.35 - 0.45 (- 0.5) cm wide when spread; leaf sheath (0.5 -) 0.8 - 1.6 (- 2.3) cm long, (0.3 -) 0.4 - 0.6 cm Ø, green, sometimes paler, fawn tinged; leaf blade (1.5 -) 2 - 6 (- 6.5) cm long, (1 -) 1.5 - 3 (- 3.2) cm wide, broadly ovate, ovate to oblong ovate, apiculate at apex, green above, paler beneath. Inflorescence (8 -) 10-22 cm long; raceme (3 -) 5 - 14 cm tall, 30 - 50 (- 60)-flowered; peduncle 5 - 8 cm long. Sterile bracts about 3 - 6, 2 - 35 mm long, 1.5-2 mm wide. Floral bracts 1.2-2 mm long, 0.6 - 1.3 mm wide. Ovary 0.6 - 1.5 mm long, 0.4 - 0.8 mm 0; pedicel 0.4 - 1 (- 2) mm long, 0.2 - 0.4 mm 0; sinuate, green. Flowers 5-5.2 mm long, ca. 4 mm wide; white and green, tinged with red or brown, to dark purple, lip yellowish to whole mauve to purple. Dorsal sepal 2.5 - 3 mm long, 1.2 - 1.4 mm wide, erect, oblong ovate to oblong. Lateral sepals 2.1 - 2.4 mm long, 1.4 - 1.6 mm wide. Petals 2.6 - 2.8 mm long, 0.7 - 0.8 mm wide, external margin delicately ciliate. Lip (1.5 -) 1.7 - 1.8 mm long, 2.2 - 2.5 mm wide, broader than long, reaching out about 2/3 - 3/4 length of lateral sepals; lamina nearly octagonal in outline; basal auricles well developed, often with involuted edges; the middle part of lamina broadly, slightly depressed, characteristic convexities - 2 pubescent, symmetrical, reniforme cushions - reaching out of down edges of basal auricles of lip; distal margins of lamina nearly truncate, with round apex at the middle part. Gynostemium 1.1 -1.4 mm long; column 0.4 - 0.5 mm wide at base; rostellum 0.7 - 0.8 mm long, 0.4 - 0.5 mm wide, transversely flabellate, basal edge narrowly incurved; stigma in widely opened, deep pocket; anther 0.4 - 0.5 mm long, 0.45 - 0.5 mm wide, 0.25 - 0.3 mm high, slightly hexagonal; loculi well separated from each other. Fruit 4.5 - 6 mm long, 23-5 mm Ø.
Habitat:
Terrestrial; in leaflitter, in forests. Alt.: 450 - 1800m.
Note:
Stanford (mscr.) mentioned that petals of the species have ciliolate margins. The cilia are very thin and delicate. Therefore, sometimes in worse preserved (dry or even conserved in liquid) materials ciliation can be hardly visible.
Distribution:
São Tomé, S. Cameroon to Equatorial Guinea
References:
Exell A.W., 1944: Catalogue of the vascular plants of S. Tome (with Principe and Annobon): 320-321. - London: British Museum.
Summerhayes 1937: Africa Orchid, 9. - Kew Bull. 1937: 457-466.
Summerhayes 1956: - In Troupin, FI. Spermolt. Parc Nat. Garamba (Explor. Parc Nat. Garamba Miss. H. de Saeger, Fasc. 4.) 1. Gymnosp. & Monocot.: 258.
Szlachetko D.L, Margonska H.B., Kras M & Kowalkowska A., 2006 (in press): Contribution to the Orchid flora of West Central Africa. Vol. 2. - Krakow. Institut of Botany, Polish Academy of Sciences.
Szlachetko & Olszewski (2001). Orchidaceae. - In: Morat P. (ed.): Flore du Cameroun 2. 36: 322-670 + 130 maps. - Paris: Museum National d’Histoire naturelle & Yaounde: Herbier National.
Images:
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