| 1 | Leaves with opposite and decussate phyllotaxy, although sometimes displaced |
| 1' | Leaves with verticillate phyllotaxy, usually ternate or quaternate, sometimes up to 8-verticillate, sometimes displaced to irregular spirals |
| 2 | Inflorescence a pedunculate umbel of 2 or more triads or tetrads 3 |
| 2' | Inflorescence other than a pedunculate umbel of triads or tetrads (e. g., a head, simple umbel, solitary flower or sessile cluster) |
| 3 | Flowers in triads |
| 3' | Flowers in tetrads |
| 4 | Triads with all flowers closely sessile |
| 4' | Triads with at least the lateral flowers pedicellate, sometimes very shortly.... |
| 5 | Corolla 4-merous |
| 5' | Corolla 5- or 6-merous |
| 6 | Leaves sessile or with a short obscure petiole rarely 3 mm long |
| 6' | Leaves with distinct petioles mostly more than 4 mm long |
| 7 | Leaves almost orbicular, cordate at the base |
| 7' | Leaves mostly ovate or obovate (rarely narrower), attenuate or cuneate at the base |
| 8 | Flowers in a linear row in the triad, the bracts not together forming a cupule subtending the triad; rays in the umbel 2-4 . |
| 8' | Flowers in an equilateral disposition in the triad, the bracts together forming a subtending cupule; rays in the umbel 5-8 |
| 9 | Rays in the umbel 2-5 |
| 9' | Rays in the umbel 6 or more |
| 10 | Leaves curvinerved; haustorial attachments lacking epicortical runners |
| 10' | Leaves pinninerved; haustorial attachments on epicortical runners |
| 11 | Inflorescence axis and rays tomentose; ovary white- or pale brown-tomentose in the lower part, glabrous above. . |
| 11' | Inflorescence axis and rays glabrous; ovary glabrous or with a uniformly sparse indumentum . |
| 12 | Corolla 4-merous |
| 12' | Corolla mostly 5-merous |
| 13 | Leaf lamina mostly less than 1 cm wide |
| 13' | Leaf lamina mostly more than 2 cm wide |
| 14 | Leaf lamina10—15 cm long; corolla 35-40 mm long |
| 14' | Leaf lamina less than 8 cm long; corolla 15-20 mm long |
| 15 | Floral bract with a complex dorsal protuberance; inflorescence peduncle very slender, more than 18 mm long |
| 15' | Floral bract constricted near the apex forming a simple dorsal protuberance; inflorescence peduncle slender to robust, less than 18 mm long |
| 16 | Inflorescence parts robust; bracts of the lateral flowers of the triads appressed to the ovary and enclosing it in early bud stages |
| 16' | Inflorescence parts slender; bracts of the lateral flowers spreading |
| 17 | Leaves dull on both sides; corolla 14-20 mm long; inflorescence and ovary glabrous |
| 17' | Leaves usually more lustrous or glossy above; corolla 20-40 mm long; inflorescence and ovary usually shortly tomentose |
| 18 | Rays in the umbel 15 or more, arising from depressions in a globular dilation of the peduncle apex . |
| 18' | Rays in the umbel 6-12, not arising from depressions in a dilated peduncle apex or if so then the dilation not globular |
| 19 | Corolla 4-merous; inflorescence peduncle distinctly widened upwards |
| 19' | Corolla 5- or 6-merous; inflorescence peduncle not widened upwards |
| 20 | Corolla in mature bud 14-20 mm long |
| 20' | Corolla in mature bud more than 25 mm long |
| 21 | Rays of the umbel 4-8; bracts of the lateral flowers of the triads c. 3 mm long, appressed to the ovary and enclosing it in early bud stages. |
| 21' | Rays of the umbel 7-12; bracts of the lateral flowers up to 2 mm long, spreading . |
| 22 | Tetrads with all flowers sessile; petals coherent at the base into a tube 4-5 mm long |
| 22' | Tetrads with three flowers shortly pedicellate; petals coherent at the base into a tube 10-12 mm long |
| 23 | Inflorescence a pedunculate or sessile 6-flowered head formed from two sessile triads |
| 23' | Inflorescence not as above (a pedunculate or sessile simple umbel, a solitary flower or a head of 3-5 flowers) |
| 24 | Corolla 4-merous; central bracts of the triads c. 6 mm long |
| 24' | Corolla 5- or 6-merous; central bracts of the triads less than 3 mm long |
| 25 | Inflorescence a simple umbel |
| 25' | Inflorescence a single flower, usually on an articulate pedicel |
| 26 | Peduncle of the umbel obsolete or up to 1 mm long; leaf lamina weakly pinni- nerved, the main lateral veins diverging from near the base... |
| 26' | Peduncle of the umbel distinct, usually more than 2 mm long; leaf lamina distinctly curvinerved from the base |
| 27 | Leaves 4-7 cm long, acuminate acute, almost sessile; articulate peduncle c. 3 mm long |
| 27' | Leaves 1.8-4 cm long, rounded, distinctly petiolate; articulate peduncle 4-8 mm long |
| 28 | Inflorescence a 2- to 4-flowered simple umbel |
| 28' | Inflorescence a pedunculate umbel of 2 or more triads or tetrads |
| 29 | Flowers in tetrads |
| 29' | Flowers in triads |
| 30 | Triads with at least the lateral flowers pedicellate |
| 30' | Triads with all flowers sessile |
| 31 | Rays in the umbel 2 or 3; leaf lamina linear-lanceolate, concave above, less than1 cm wide |
| 31' | Rays in the umbel 4-8; leaf lamina lanceolate to nearly orbicular, flat, more than 1 cm wide |
| 32 | Leaves mostly in regular whorls of 5 or 6, rarely quaternate... |
| 32' | Leaves ternate or rarely quaternate, frequently scattered |
| 33 | Leaves sessile or sometimes with a very short thick petiole.. |
| 33' | Leaves distinctly petiolate |
