| 1 | Leaves in whorls of 3 or more |
| 1' | Leaves opposite |
| 2 | Leaves densely pubescent all over beneath |
| 2' | Leaves glabrous or only pubescent on midrib and secondary veins beneath |
| 3 | Corolla tube ≥ 10 mm long |
| 3' | Corolla tube < 8 mm long |
| 4 | Corolla tube pubescent in throat |
| 4' | Corolla tube glabrous in throat |
| 5 | Corolla campanulate |
| 5' | Corolla subcylindrical, salverform, rotate or urceolate |
| 6 | Hairs on corolla tube dense rufous brown |
| 6' | Hairs on corolla tube very short and cream coloured or pale fawn, or corolla tube glabrous outside |
| 7 | Tips of corolla lobes glabrous outside; flowers densely clustered at inflorescence ends |
| 7' | Tips of corolla lobes pubescent outside; flowers laxly arranged or clustered |
| 8 | Corolla tube ≥ 5.4 mm long. — Not in New Guinea |
| 8' | Corolla tube < 6 mm long. — Those > 3 mm long only in New Guinea |
| 9 | Corolla tube somewhat inflated, wider than head in bud; anthers with large boss on the back |
| 9' | Corolla tube not inflated, narrower or same width as head in bud; no large boss on anthers |
| 10 | Hairs on inflorescence spreading |
| 10' | Hairs on inflorescence appressed |
| 11 | Leaf base cuneate to obtuse |
| 11' | Leaf base cordate |
| 12 | Inflorescence 14-20 cm long; mature corolla tube c. 2 mm wide |
| 12' | Inflorescence 3.5-13 cm long; mature corolla tube 3-4 mm wide |
| 13 | Corolla tube glabrous outside, lobes 3.9-5.6 times as long as tube, strongly reflexed when mature. — Lesser Sunda Islands |
| 13' | Corolla tube puberulent or glabrous outside, lobes 0.7-2.2 times as long as tube, erect or spreading when mature. — Widespread |
| 14 | Stamens subsessile or with very short filaments. — New Guinea |
| 14' | Stamens with well-developed filaments. — Widespread |
| 15 | Leaves without prominent venation; disk lobes free |
| 15' | Leaves with prominent venation above; disk lobes fused |
| 16 | Corolla pinkish or reddish, with a rounded or apiculate head in bud; fruit spiny |
| 16' | Corolla yellow, with an acuminate head in bud; fruit smooth |
| 17 | Filaments twisted around the style |
| 17' | Filaments straight or, if bent, not twisted around the style |
| 18 | Flowers hour-glass-shaped; corolla tube > 7 mm long |
| 18' | Flowers not hour-glass-shaped; corolla tube < 6 mm long |
| 19 | Flowers fleshy, corolla lobes strongly overlapping in bud; sepal lobes rounded to obtuse |
| 19' | Flowers not fleshy, corolla lobes only slightly overlapping or appearing valvate in bud; sepals acuminate to obtuse |
| 20 | Anthers exserted completely beyond mouth of corolla tube; lobes 2.4-5.6 times as long as tube |
| 20' | Anthers partially included in corolla tube or located at mouth of corolla tube; lobes 0.4-3.1 times as long as corolla tube |
| 21 | Inflorescence delicate, with flowers clustered at inflorescence branch ends forming rounded heads; fruits fusiform, ≤ 12 cm long. — Lesser Sunda Islands |
| 21' | Inflorescence more robust, flowers not forming rounded heads; fruits linear, ≥ 15 cm long. — Moluccas, New Guinea |
| 22 | Filaments with large projections on the sides; dried leaves usually somewhat glaucous beneath |
| 22' | Filaments without large projections on the sides; dried leaves not glaucous |
| 23 | Corolla bearded in throat with brown hairs, usually densely brown pubescent outside, rarely glabrous |
| 23' | Corolla glabrous or pale-coloured pubescent in throat and glabrous, brown papillose or shortly puberulent outside |
| 24 | Sepals erect or only slightly spreading at apex; corolla tube 4.2-5.4 mm long |
| 24' | Sepals strongly reflexed; corolla tube 1.9-4.5 mm long |
| 25 | Leaf base cuneate, rarely to obtuse; leaves 1.8-4.8 times as long as wide |
| 25' | Leaf base cordate to rounded; leaves 1.1-2 times as long as wide |
| 26 | Inflorescence 2.7-6.7 cm long; corolla tube 1.9-2.2 mm long. — Java to Flores |
| 26' | Inflorescence 7-18.5 cm long; corolla tube 2.9-3.2 mm long. — Bismarck Archipelago |
| 27 | Corolla with downward pointing hairs in throat |
| 27' | Corolla glabrous or with upward pointing hairs in throat |
| 28 | Open corolla campanulate or subcampanulate |
| 28' | Open corolla salverform or with narrow tube and erect lobes |
| 29 | Tertiary venation densely reticulate |
| 29' | Tertiary venation largely obscure, occasionally slightly prominent |
| 30 | Corolla lobes 1.8-3.1 times as long as tube |
| 30' | Corolla lobes 0.7-1.3 times as long as tube |
| 31 | Inflorescence pubescent all over; corolla tube 1.3-2 mm long; leaves 1-5.1 cm long |
| 31' | Inflorescence pubescent only in upper parts; corolla tube 2-3.4 mm long; leaves 2.1-10.8 cm long |
| 32 | Corolla tube much narrower than corolla bud head |
| 32' | Corolla tube wider than to more or less same width as corolla bud head |
| 33 | Tertiary venation densely reticulate; leaves usually drying dull ochre above |
| 33' | Tertiary venation obscure or only laxly reticulate; leaves not drying dull ochre above |
| 34 | Buds ovoid in shape; often papillose outside; disk entire |
| 34' | Buds cylindrical or club-shaped; not papillose outside; disk usually of 5 separate lobes |
| 35 | Inflorescence 3-21 cm long, flowers not forming a dense rounded cluster at ends |
| 35' | Inflorescence 1.1-4 cm long, flowers forming a dense rounded cluster at ends |
