| 1 | Foliar organs conspicuous and numerous at anthesis, divided into narrowly linear to capillary segments, the ultimate segments bearing apical and often lateral solitary or fasciculate setulae. |
| 1' | Foliar organs simple, orbicular to linear, never setulose, often not present or conspicuous at anthesis. |
| 2 | Turions (winter buds) of tightly clustered modified foliar segments present at the apex of some of the stolons. |
| 2' | Turions not present. |
| 3 | Turions glabrous or almost so. Ultimate foliar segments with minute apical but with or without icroscopic lateral setulae |
| 3' | Turions densely setulose. Ultimate foliar segments with ± numerous lateral setulae. |
| 4 | Primary foliar segments 3 or more semi-verticillate on the stolons usually with hyaline or foliose etulose stipule-like segments at the base. Scales on peduncle absent. |
| 4' | Primary foliar segments 1 or 2 usually without stipule-like segments at the base. Scales (or at least one) present on the peduncle. |
| 5 | Peduncle with a whorl of inflated ellipsoid floats some distance above the base. Basal segments of oliar organs hyaline. |
| 5' | Peduncle without floats or with a whorl of narrowly fusiform floats at the base. Basal segments of foliar organs foliose |
| 6 | Floats shortly stipitate with capillary foliar segments at the base. Capsule much longer than the calyx lobes. Seeds thinly lenticular with a single marginal wing |
| 6' | Floats sessile without foliar segments at the base. Capsule shorter than the calyx. Seeds prismatic, narrowly winged on the angles. Africa, Madagascar, SE. Asia, Australia. |
| 7 | Foliar organs less than 10 mm long with few (2-10) ultimate segments with few or no lateral setulae. |
| 7' | Foliar organs more than 20 mm long with very numerous ultimate segments bearing ± numerous lateral setulae. |
| 8 | Ultimate segments distinctly flattened with microscopic or no lateral setulae. Bracts and scales auriculate, the scales few but dispersed through the length of the peduncle. Spur of the corolla very short, saccate. Capsule circumscissile. Seeds prismatic |
| 8' | Ultimate segments terete, sometimes with a few lateral setulae. Bracts and scales not auriculate, scales usually only one near the middle of the peduncle. Spur of the corolla narrowly conical. Capsule laterally bivalvate. Seeds lenticular, winged |
| 9 | Ultimate segments terete. Traps absent from the lowermost part of the foliar organs. Bracts and scales medifixed, the scales disposed through the length of the peduncle. Corolla mauve or white. Seeds with a broad dentate wing |
| 9' | Ultimate segments distinctly flattened. Traps present in the lowermost part of the foliar organs and with rudimentary traps at the very base. Bracts and scales basifixed, slightly auriculate, the scales few and usually present only in the upper part of the peduncle. Corolla yellow. |
| 10 | Bracts medifixed or produced below the point of attachment. |
| 10' | Bracts basifixed. |
| 11 | Bracteoles present. |
| 11' | Bracteoles absent. |
| 12 | Calyx lobes approximately equal in size. Foliar organs linear to narrowly obovate, usually not conspicuous at anthesis |
| 12' | Calyx lobes very unequal in size, the upper much larger. Foliar organs reniform to obovate, usually present and ± conspicuous at anthesis. |
| 13 | Corolla lower lip 3-lobed, the lateral lobes obliquely emarginate, spur c. 2 mm long. Seeds ovoid, densely echinate |
| 13' | Corolla lower lip ± regularly 5-lobed, spur at least 5 mm long. |
| 14 | Spur over 10 mm long, usually longer than and widely diverging from the lower lip of the corolla. Flowers 1 or 2. Peduncle up to 6 cm long, relatively stout |
| 14' | Spur c. 5 mm long, usually about as long as and ± parallel with the lower lip of the corolla. Flowers up to 10. Peduncle up to 15 cm long, very slender. Seeds pyriform, glochidiate. |
| 15 | Lower lip of corolla deeply 2-lobed, corolla pink or white. Pedicel minutely papillose. Seeds globose with distinct coarse isodiametric reticulation |
| 15' | Lower lip of corolla deeply 3-lobed, corolla yellow. Pedicel smooth. Seeds ellipsoid with indistinct coarse very elongate reticulation |
| 16 | Bracteoles absent. Lower calyx lobe much longer than upper in fruit. |
| 16' | Bracteoles present. Calyx lobes ± equal or upper longer. |
| 17 | Bracteoles not much narrower (at least half as wide) than the bract. |
| 17' | Bracteoles much narrower (less than one quarter as wide) than the bract. |
| 18 | Calyx, peduncle and pedicels ± densely covered with often long septate hairs. |
| 18' | Calyx glabrous. Peduncle glabrous or with a few short septate hairs. |
| 19 | Lower lip of corolla deeply 4-lobed. Corolla yellow |
| 19' | Lower lip of corolla entire, emarginate or ± 3-lobed. |
| 20 | Corolla yellow. |
| 20' | Corolla mauve or white. |
| 21 | Peduncle twining. |
| 21' | Peduncle erect. |
| 22 | Corolla (11—)15—20 mm long, upper lip orbicular, much wider than the calyx lobes. |
| 22' | Corolla 5-10 mm long, upper lip oblong, narrower than the calyx lobes. |
| 23 | Lower lip of corolla 3-lobed, corolla 15-22 mm long |
| 23' | Lower lip of corolla entire or emarginate, corolla 6-10 mm. Pedicels strongly recurved in fruit |
| 24 | Peduncle twining. Pedicels strongly reflexed in fruit |
| 24' | Peduncle erect. Pedicels erect or spreading in fruit |
