AFRICAN

ORCHIDS

Orestias foliosa Summerh. in G.M.D.Troupin, Fl. Spermatophyt. Parc Nat. Garamba 1: 258 (1956).
Description:
Plants (10 -) 15 - 25 cm tall, few to many compactly clustered. Rhizome few mm long between shoots, 1 - 2.6 mm Ø, sometimes branched, node scales loose. Leafy stem (5 -) 9 - 16 cm long, (0.1 -) 0.15 - 0.25 (- 0.3) cm Ø; basal scales 1.2 - 2.5 cm long, 0.18 -0.48 cm 0. Leaves (2 -) 3 (- 4); leaf petiole (0.16 -) 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 - 1.4 (- 2) cm long, (0.15 -) 0.22 - 0.45 (- 0.65) cm Ø, green, sometimes paler, fawn tinged; leaf blade (1.5 -) 2.5 - 6 (- 6.5) cm long, (I -) 2 - 3 (- 3.3) cm wide, ovate to oblong ovate, apiculate at apex, green above, paler beneath. Inflorescence (6 -) 10 - 15 (- 17) cm long; raceme (3 -) 5 -7 (- 9) cm tall, 20 - 60 (- 80)-flowered; peduncle (3 -) 6 - 8 cm long. Sterile bracts about 3 - 7, 2.5 - 4 mm long, 1.7 - 2.2 mm wide. Floral bracts 1.5 - 3.5 mm long, 0.7 - 1.5 mm wide. Ovary 1.5 - 3.2 mm long, 0.4 - 0.65 mm Ø; pedicel 1.4 - 2 mm long, 0.3 - 0.5 mm Ø; sinuate, green. Flowers (4 -) 4.5 - 5 mm long, (3.2 -) 3.5 - 4 mm wide; white and green tinged with red or brown, to dark purple, lip yellowish to whole mauve to purple. Dorsal sepal 1.5 - 2 (- 2.5) mm long, 0.8 - 1 (- 1.2) mm wide, erect, oblong ovate to oblong. Lateral sepals 1.5 - 1.6 (- 1.8) mm long, I - 1.3 (- 1.5) mm wide. Petals (1.8 -) 2 (- 2.2) mm long, 0.4 - 0.5 (- 0.65) mm wide. Lip 1.3 - 1.5 (- 1.7) mm long, 1.4 - 1.5 (- 1.8) mm wide, slightly broader than long, reaching out about 2/3 length of lateral sepals; lamina nearly hexagonal in outline; basal auricles well developed, often with involuted edges; the middle part of lamina broadly depressed, characteristic convexities - 2 pubescent, symmetrical cushions - reaching out of down edges of basal auricles of lip, each of them reniform; lamina at distal margins transversely oblong, sometimes with weak apiculate apex. Gynostemium 1.3 - 1.5 mm long; column 0.35 - 0.5 mm wide at base; rostellum (0.4 -) 0.5 - 0.6 mm long, 0.25 - 0.32 mm wide, transversely flabellate, basal edge narrowly incurved; stigma in widely opened, deep pocket; anther 0.35 - 0.4 mm long, 0.37 - 0.42 mm wide, 0.25 - 0.3 mm high, trapezoid, the distal edge shorter; loculi distinctly separate from each other. Fruit 4.8 - 6.4 mm long, 3 - 5.2 mm Ø.
Habitat:
Terrestrial; in leaflitter; in gallery forest; on very humid sandy soil, in exploited high forest. Alt.: 25 - 800 m.
Note:
O.foliosa can be easily distinguished by the lip being slightly broader than long, nearly hexagonal in outline; pubescent convexity reaching out of down edges of basal auricles of lip; lip reaching out only about 2/3 length of lateral sepals.
Distribution:
WC. Trop. Africa
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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