| 1 | Flowers 4-merous (rarely 3- or 5-merous), petals < 0.5 cm long |
| 1' | Flowers 6(-7)-merous, petals 0.1 cm to several cm long |
| 2 | Inflorescence determinate, single terminal flower following at least one pair of monads |
| 2' | Inflorescence indeterminate (i.e., lacking a terminal flower), consisting of lateral, bracteolate triads only |
| 3 | Flowers usually bright yellow (not red), each subtended by a separate green, foliar bract(eole); known from Mt. Roraima summit only |
| 3' | Flowers not bright yellow, and not separately subtended by foliar bract(eole)s; diverse localities |
| 4 | Inflorescence with lateral monads only, including sessile monads |
| 4' | Inflorescence with lateral triads or dyads only |
| 5 | Flowers mostly partially immersed in inflorescence axis, each flanked by 2 strap-like, nearly obscured, bracteoles; pollen with 3 prominent excavations on each face |
| 5' | Flowers not immersed in inflorescence axis; bracteoles not strap-like, ca. boat-shaped, largely exposed; pollen lacking prominent excavations |
| 6 | Petals > 4 cm long, usually reddish or red and yellow; seed lacking endosperm |
| 6' | Petals < 2 cm long, white, cream-colored or red; seed with endosperm |
| 7 | Flowers unisexual, plants dioecious |
| 7' | Flowers bisexual |
| 8 | Anthers basifixed, longer filaments laterally excavated to accommodate lower anthers |
| 8' | Anthers dorsifixed, versatile, filaments slender, not laterally excavated |
| 9 | Triads and flowers stalked; anthers dorsifixed, versatile |
| 9' | Triads and flowers sessile or essentially so; anthers basifixed, longer filaments laterally excavated to accommodate lower anthers |
