1.	Flowers blue–white or blue–green. Japan	2
	Flowers orange–brown or orange–brown and green. Central Africa	4
2.	Staminal filaments strongly dorsiventrally flattened, subfoliose, margins deeply toothed; terminal style-stigma with three acute branches, style appendages each bifurcate, apices acute	1. O. yamashitae
	Staminal filaments subcylindrical, margins entire; style-stigma and style appendages with apices clavate or capitate, rounded	3
3.	Perianth lobes filiform; base of lobes with callus-like cluster of round cells on the adaxial surfaces	2.O. shinzatoi
	Perianth lobes narrowly triangular at base; base of lobes smooth	3.O. hyodoi
4.	Perianth lobes narrowly triangular; tube about as long as wide	4.O. duncanii
	Perianth lobes filiform; tube about twice as long as broad	5
5.	Perianth lobes brown, c. 10 mm long; tube orange-brown. Cameroon	5.O. triandra
	Perianth lobes white, c. 5 mm long; tube dark green, base orange brown. C.A.R	6.O. frankei