KEY TO THE SPECIES

1Stamens included; filaments ≥ 30 mm long
1'Stamens exserted; filaments < 30 mm long
2Sepals 9-20(-30) mm long; lower part of corolla tube 5-10 mm long; filaments inserted at 10-15(-20) mm from corolla base
2'Sepals 24-40(-45) mm long; lower part of corolla tube (10-)15-17.5 mm long; filaments inserted at 20-25 mm from corolla base