1. Leaves less than 3 mm wide; inflorescences 1-flowered, surrounded by 3 bracts; thorns furcate or forked at apex..............B. spinosa

1. Leaves more than 3 mm wide; inflorescences 3-flowered, surrounded by 3 bracts; thorns simple.

2. Bracts 2.5–4.5 cm long, usually strikingly colored; perianth lobes inconspicuous, white or cream.

3. Leaves thick, leathery .........................................................................................................................................................B. pachyphylla

3. Leaves thin and papery, especially when dry.

4. Leaves and perianth tube glabrous; apex of bracts usually obtuse or rounded...........................................................B. peruviana

4. Leaves and perianth tube variously pubescent; apex of bracts acute or acuminate.

5. Leaves densely villous; perianth tube short villous...................................................................................................B. spectabilis

5. Leaves merely puberulent; perianth tube sparsely to densely puberulent

6. Anthocarp oblong...............................................................................................................................................................B. glabra

6. Anthocarp obconical-obturbinoid to fusiform............................................................................B. glabra var. obtusibracteata

2. Bracts 1–2.5 cm long, normally unostentatious; perianth lobes somewhat conspicuous, bright yellow, green, or red.

7. Perianth tube 6–7 mm long, campanulate, gradually widening from base to apex...................................................B. campanulata

7. Perianth tube 9–25 mm long, hypocrateriform or infundibuliform, slightly or highly constricted distally or in middle

8. Perianth tube ca. 1.5 mm wide, glabrous, reddish....................................................................................................B. berberidifolia

8. Perianth tube broader >1.5 mm wide, variously pubescent, greenish-brown or greenish-yellow.

9. Perianth tube 9–11 mm long, densely tomentulose

10. Perianth tube base ellipsoid, constricted in the middle...........................................................................................B. praecox

10. Perianth tube almost straight or slightly constricted..............................................................................................B. modesta

9. Perianth tube 12–25 mm long, densely pubescent or puberulent

11. Perianth tube densely pubescent; ovary navicular....................................................................................................B. infesta

11. Perianth tube puberulent; ovary spindle-shaped...................................................................................................B. stipitata