| 1 | Papillae on the lower leaf surface indistinct or obscure. Petals valvate, glabrous |
| 1' | Papillae on the lower leaf surface usually distinct. Petals imbricate, hairy outside. |
| 2 | Papillae in small groups in the areolae |
| 2' | Papillae rather uniform, not separated into groups as above. |
| 3 | Veins of leaves reticulate-scalariform |
| 3' | Veins of leaves reticulate, some cross-bar-like. |
| 4 | Leaves densely, sometimes sparsely tomentose or pubescent, glabrescent, rarely glabrous on the lower surface |
| 4' | Leaves glabrous, sometimes sparsely puberulous beneath |
