1	Plant always pale yellow or whitish; stigma flattened, widely concave, reniform to disciform, very shallowly 2-lobed; upper lip porrect (continuing the dorsal line of the corolla tube)	2
-	Plant usually strongly pigmented, rarely yellowish; stigma deeply divided into distinct subspherical lobes; upper lip erect or recurved	3
2	Stems short and stout, up to 40×1.2 cm; inflorescence usually dense, club-like; flowers patent; calyx-segments usually unequally bidentate; corolla with a regularly and strongly arched-curved dorsal line (straight in the apical third); corolla lips with coarsly eroded-denticulate margin; on Aconitum	O. lycoctoni
-	Stems more slender, up to 45×0.7 cm; inflorescence laxer; flowers erecto-patent; calyx-segments often entire or more unequally bidentate; corolla with an almost regularly curved dorsal line (straight only near the apex); corolla lips with finely eroded-denticulate margin; on Thalictrum	O. krylowii
3	Corolla with distally straight dorsal line, with a distinctly flattened subapical area; lower lip cruciform, with concave, spathulate, very divergent lobes; on Centaurea and Echinops	O. kochii
-	Corolla with regularly curved dorsal line; lower lip with less divergent, elliptic or rounded and flat to convex lobes	4
4	Apex of the inflorescence acute, due to the appressed bracts with a comose appearance; flowers erecto-patent, tubular-infundibuliform; corolla variably (pink, reddish, yellow), but always vividly pigmented; filaments hairy almost to the apex; on Ranunculaceae (Helleborus) and Lamiaceae (Phlomis, Sideritis)	O. haenseleri
-	Apex of the inflorescence rounded, with no crown of bracts; flowers patent, tubular to wide-tubular; corolla brownish, purple or reddish to yellowish brown, rarely yellow, but usually feebly pigmented; filaments hairy at most in its lower two thirds	5
5	Plants up to 85 cm, tall and stout; inflorescences long, cylindrical, often covering the upper two thirds of the stem; corolla with dorsal line regularly curved, sometimes more or less deflexed at the apex; upper corolla lip shallowly emarginate; mainly on Centaurea	O. elatior s. str.
-	Plants up to 60 cm, usually shorter and more slender, with relatively narrower stems; oval inflorescences, dense, at most covering the upper half of the stem; corolla with regularly and strongly curved dorsal line, but somewhat straight at the apex; upper corolla lip more deeply and distinctly emarginate; on Apiaceae (mainly on Peucedanum)	O. alsatica