| 1 | Annuals |
| 1' | Perennials |
| 2 | Flowers sessile or subsessile; capsule hirsute |
| 2' | Flowers distinctly stalked; capsule glabrous |
| 3 | Corolla 1.5-2.8 cm diam., pink or purplish; lower leaves broadly cordate or reniform, upper often lobed; seeds 3-4 mm long |
| 3' | Corolla not more than 1.5 cm diam., blue; upper leaves not lobed; seeds c. 2-2.5 mm |
| 4 | Leaves oblong or narrowly cordate, distinctly petiolate |
| 4' | Leaves narrowly obovate or oblanceolate, sessile or narrowed to an indistinct petiole |
| 5 | Climbing or trailing herbs; rootstock usually not woody |
| 5' | Erect or suberect herbs or subshrubs; rootstock usually woody |
| 6 | Upper cauline leaves deeply palmatisect |
| 6' | Upper cauline leaves not palmatisect |
| 7 | Leaves oblong, oblanceolate or elliptic |
| 7' | Leaves cordate or hastate |
| 8 | Plants glabrous or very sparsely pubescent; corolla up to 3 cm diam. |
| 8' | Plants hairy or distinctly pubescent; corolla often more than 3 cm diam. |
| 9 | Stems woody, persistent |
| 9' | Stems herbaceous, dying back in winter |
| 10 | Sepals clothed with spreading hairs |
| 10' | Sepals clothed with adpressed hairs |
| 11 | Plant erect, 30-60 cm high; inflorescence almost leafless with numerous, divaricate branches |
| 11' | Plant decumbent, less than 30 cm high; inflorescence terminal on sparsely branched leafy stems |
| 12 | Sepals clothed with adpressed hairs |
| 12' | Sepals clothed with spreading hairs |
