Key to the species of Helixanthera

1Corolla more than 15 mm long
1'Corolla less than 13 mm long
2Pedicels flattened, winged and widened upwards; corolla 6-merous..
2'Pedicels angular but not flattened or winged; corolla 5-merous
3Pedicel shorter than ovary; inflorescence axis 20-60 mm long
3'Pedicel mostly longer than the ovary; inflorescence axis 50-250 mm long
4Style reaching to the top of the anthers; inflorescence axis less than 70 and often less than 50 mm long
4'Style reaching only to near the base of the anthers; inflorescence axis more than 60 and often more than 100 mm long
5Flowers sessile; petals commonly 5, sometimes 4
5'Flowers pedicellate, sometimes very shortly; petals 4
6Leaves rounded at the apex; inflorescence axis up to 40 mm long; corolla rounded in bud, 3.5-5 mm long; anther shorter than the free filament
6'Leaves acute at the apex; inflorescence axis more than 45 mm long; corolla acute in bud, 5-7 mm long; anther longer than the free filament
7Inflorescence of 10-30 flowers distributed along an axis 15-70 mm long; free filament longer than the anther
7'Inflorescence of 2-5 flowers subumbellately crowded near the tip of an axis 5-20 mm long; free filament much shorter than the anther
8Style angular in the lower part below a constriction near the middle, more slender above
8'Style terete or angular, gradually widened upwards, lacking a constriction....
9Flowers sessile; bracts strongly reflexed, with a dorsal spur-like sac; style weakly constricted
9'Flowers pedicellate, sometimes very shortly; bracts not strongly reflexed, sometimes with a dorsal transverse fold but lacking a sac; style strongly constricted..
10Inflorescence sometimes subtended by an involucre of a few narrow bracts up to 5 mm long; ovary barrel-shaped or shortly cylindric, usually with irregular wrinkles or furrows persisting to the young fruit; corolla 3.5-8.5 mm long
10'Inflorescence subtended by an involucre of numerous linear bracts up to 15 mm long; ovary cylindric, longer than wide, usually slightly narrowed below the calyx limb, sometimes longitudinally weakly angled or furrowed; corolla 7-12 mm long