Kleinsteuber, A., Ristow, M. & Hassler, M., Flora von Rhodos und Chalki 1. 2016Meikle, R.D., Flora of Cyprus 2. 1985
Taxonony of the genus (except B. tenuiflora) far from being clarified in and outside Cyprus. The key is based on the cited sources but much modified. It needs further testing.
1Corolla-limb minute, c. 2 mm diam.; inflorescence hairs yellowish; flowers crowded at anthesis, with bracts neatly arranged in two rows; nutlets with distinct lateral swellings
1'Corolla-limb 3-4 mm (or more) diam.; inflorescence hairs white or greyish; flowers not crowded, nor the bracts neatly arranged; nutlets without obvious lateral swellings
2Pedicels cylindrical, straight; gynobasis horizontal; corolla-limb milky white
2'Pedicels (at least when fruiting) thickened, slightly curved; gynobasis oblique; corolla-limb blue or milky white
3Erect annual of mostly anthropogenous habitats, usually more than 15 cm high; calyx often strongly accrescent after anthesis; nutlets 3 mm long
3'Prostrate or decumbent annual of (semi-)natural high mountain habitats, usually less than 10 cm high; calyx not much accrescent after anthesis; nutlets 2 mm long
4Adaxial nutlets embedded in the receptacle and pedicel (hard to remove); nutlets with small, low tubercles; corolla-limb blue; prostrate or decumbent annual of (semi-)natural mountain habitats
4'Adaxial nutlets less embedded in the receptacle and pedicel (easy to remove); nutlets with prominent tubercles; corolla-limb (always?) milky-white; (always?) erect annual of mostly anthropogenous habitats