Bonatea rabaiensis (Rendle) Rolfe in D.Oliver & auct. suc. (eds.), Fl. Trop. Afr. 7: 253 (1898).
Habenaria rabaiensis Rendle, J. Linn. Soc., Bot. 30: 390 (1895).
Erect, decumbent or scandent terrestrial herbs, 200-593 mm tall; tubers 2-4, spreading, elongate-oblong, tomentose. Stem slender, 195-583 x 1.5-6.0 mm. Leaves 3-10, lax, cauline, lower sheathing, blades reduced, oblanceolate to elliptical-lanceolate, acute, mucronate, margins entire, smooth, 40-138 x 14-46 mm. Inflorescence cylindrical, 65-143 x 58-131 mm, lax, 1-7-flowered; bracts sometimes withered at flowering, similar to upper leaves, sheathing, lanceolate to ovate-lanceolate, apiculate, 15.5-38.5 x 4.0-11.5 mm. Flowers spreading, green and white, pedicel and ovary sub-erect, 3147 mm long. Dorsal sepal green, erect, elliptical to oblong-ovate, galeate, acute to acuminate, 13.5-22.0 x 5.5-7.5 mm; lateral sepals green, projecting forwards, strongly deflexed, ovate-lanceolate, apiculate, base oblique, margins weakly to strongly revolute, 10.5-19.0 x 6-9 mm, adnate to lip and stigmatic processes for 6.0-10.5 mm. Petals upper lobe erect, linear, acute to acuminate, 13.5-19.5 x 0.52.0 mm, adnate to dorsal sepal, lower lobe spreading horizontally, weakly to strongly deflexed, Iinear-falcate, tip curved, acuminate to apiculate, 15.0-31.5 x 0.5-1.5 mm, adnate to claw of lip for 4-10 mm. Lip green, claw 10.0-18.5 mm, median lobe descending, geniculate, apically recurved, linear-lanceolate to narrowly-oblong, acute to acuminate, 9.0-16.5 x 0.5-1.5 mm, lateral lobes descending, diverging, linear-falcate, tips curved, acuminate, 17.0-33.5 x 0.5-1.5 mm; spur toothless, 49-68 mm long, clavate apex 20-31 mm long. Anther erect, apiculate, 4.5-10.0 mm long, canals slender, 10-17 mm long. Stigmatic processes clavate, projecting forwards and deflexed, sub-parallel, 14.5-18.5 mm long, base adnate to lip. Rostellum 3lobed, base auriculate, median lobe cucullate, apex incurved, apiculate, margin ciliate, 6.5-9.5 mm long, lateral lobes linear, fused to anther canals, projecting forwards to sub-erect to 45°, sub-parallel, 2.0-3.5 mm long. Flowering period: May to June, rarely to August.
Forest and thicket, 50-1220 m altitude.
Bonatea rabaiensis is the only species of Bonatea to have no tooth in the mouth of the spur. This species has lateral sepals similar to Bonatea steudneri and a spur length equivalent to Bonatea pulchella. A hawkmoth of the genus Nephele, proboscis length ca. 70 mm, occurs within the coastal range of B. rabaiensis and may be a pollinator.
SE. Kenya to NE. Tanzania