AFRICAN

ORCHIDS

Gastrodia rwandensis Eb.Fisch. & Killmann, Kew Bull. 65: 317 (2010).
Description:
A leafless achlorophyllose erect herb, up to 3 – 4 cm tall; rhizome tuberous, obliquely fusiform, elongated up to 3.5 × 0.5 – 0.6 cm. Inflorescence lax, up to 1 cm long, with 2 – 3 (4) flowers; scale leaves 3, truncate with abruptly pointed apex, 5 – 7 mm long; bracts 10 × 6 mm, brown. Flowers campanulate, up to 15 mm long, light brown with darker brown and warts towards the sepal tips with a blackish lip; pedicel 5 – 8 mm long; ovary 4 – 5 mm long. Sepals and petals fused, the petals inserted on the sepals at the apex of the sepaline tube. Dorsal sepal ovate, obtuse, 12 × 6 –7 mm; lateral sepals ovate, subacute, 14 – 15 × 6 – 8 mm. Petals ovate, 6 – 7 × 4 mm. Lip obscurely 3-lobed, 8 – 9 mm long, blackish, basal part 4 × 5 mm, apical part 3 – 3.5 × 2 – 3 mm; callus of three fleshy ridges at base of midlobe, the middle ridge highest. Column 8 – 9 mm long, with 2 brownish calli at tip of the column-foot. Fruit unknown.
Habitat.
Understorey of montane rainforest; 1850 m.
Notes:
This new species differs in the much smaller habit, the brown to dark brown flowers, the larger dorsal sepal and lateral sepals, the broader petals and the ornamentation of lip with two, brownish 3 – 5- lobed calli lacking the two glandular protuberances at the apex.
The vegetation at the type locality consists of Alangium chinense and Carapa grandiflora in the tree layer, Grewia mildbraedii, Chassalia subochreata, Lepidotrichilia volkensii, Ficus asperifolia in the shrub layer, the lianas Clerodendron sp., Culcasia falcifolia and Thunbergia vogeliana, and Harveya alba and Tectaria sp. in the herb layer. Only known from Cyamudongo Forest, where a small population of about 10 plants is known at present.
Distribution:
Rwanda (Nyungwe)