| 1 | Leaves deeply 3-lobed, in shape often resembling the letter 'W'. |
| 1' | Leaves entire. |
| 2 | Leaf base not cordate, but obtuse or rounded, shallowly concave, subtruncate, or slightly cuneate. |
| 2' | Leaf base distinctly cordate. |
| 3 | Leaves glabrous beneath. |
| 3' | Leaves minutely hairy beneath especially on the venation |
| 4 | Leaves distinctly papillate beneath (handlens or binocular), 5-nerved, joined by reticulate and transverse veins |
| 4' | Leaves not papillate beneath, 3 (-5)-nerved, joined by transverse veins |
| 5 | Petiole 10-13 cm long. Flowers large: utricle 5-6 cm long, tube c. 5 cm long, limb 4-9 cm long, 3-lobed. Stamens 10 |
| 5' | Petiole much shorter. Flowers much smaller. Perianth 1-lipped. Stamens 6. |
| 6 | Leaf veins and veinlets closely foveolate-reticulate, prominent beneath. Utricle with 6 (or 2) glandular bodies inside. (Seeds not winged) |
| 6' | Leaf veins and veinlets loosely reticulate or transverse, distinct or rather faint beneath. Utricle with 2 glandular bodies inside. |
| 7 | Leaf undersurface papillate (under the binocular). Perianth without a stipe; utricle 3-6 mm long, tube 2.5-5 mm long, limb 11-12 mm long. Seeds not winged |
| 7' | Leaf undersurface not papillate. Perianth with a distinct stipe; utricle 3-9 mm long, tube 5-10 (-15) mm long, limb 20-30 (-40) mm long. Seeds distinctly winged |
