| 1 | Branches of inflorescence crowded at apex, at acute angles. Leaves greyish-white, velvety |
| 1' | Branches of inflorescence at different levels, often furcate at apex. Hairs of leaves different |
| 2 | Corolla broadly cylindrical, up to 10 mm long. Nutlets 6 mm in diam., with a dis- tinct margin |
| 2' | Corolla campanulate, funnel-shaped or rotate, shorter. Nutlets rarely up to 6 mm |
| 3 | Corolla with a short tube and a wide, rotate limb c. 8-10 mm in diam. Leaves gla-brescent, with mineralized pustules at a later state. Calyx-lobes glabrous on their outer surface |
| 3' | Corolla either of different shape and size or leaves markedly hairy, not glabrescent. Calyx-lobes hairy on outer surface |
| 4 | Nutlets 5(-6) mm long. Robust plant at least 75 cm high |
| 4' | Nutlets smaller |
| 5 | Corolla c. 12 mm in transverse diam. Plant 50-75 cm high. Nutlets c. 4-4.5 mm long |
| 5' | Corolla (and usually the whole plant) smaller. Nutlets 1.5-4.5 mm long |
| 6 | Whole plant golden silky-tomentose. Corolla white |
| 6' | Plant with different kind of hairs. Corolla blue to dark purple at least in part |
| 7 | Style distinctly shorter than nutlets. Nutlets with very short, few, slender, subulate spines, attached to the receptacle with a very small, apical areola. Lobes of corolla 3.5 mm long and wide |
| 7' | Style longer than nutlets. Nutlets with longer and usually more numerous glochids. Attachment to receptacle different. Corolla lobes smaller |
| 8 | Lowermost pedicel 1-1.5 cm long, recurved. Inflorescence few-flowered, flow- ers remote. Flowers and nutlets very small |
| 8' | Pedicels fairly equal or the lowermost pedicel a little longer, but not as much as 10 mm. Flowers more or less dense |
| 9 | Nutlets c. 1.5-2.2 mm long, with short pedicels or nearly sessile |
| 9' | Nutlets 2.5-3(-3.5) mm long, with longer or short, distinct pedicels |
| 10 | Fruiting cymes spreading, rigid, uppermost forked, lower ones subhorizontal |
| 10' | Fruiting cymes not spreading nor rigid, at least uppermost at acute angles, sub- erect |
| 11 | Corolla campanulate to funnel-shaped, up to 3 mm long. Nutlets 2-3 mm long |
| 11' | Corolla campanulate, up to 5 mm long. Nutlets 3-4 mm long |
| 12 | Pedicels filiform, recurved, longer than calyx. Nutlets c. 2-2.5 mm long |
| 12' | Pedicels stouter, recurved or patent, not longer than calyx. Nutlets 3(-3.5) mm long |
