| 1 | Sori short, on one-veined ultimate segments of much-divided fronds. |
| 1' | Sori distinctly elongate along the veins; segments of frond usually with more than one vein. |
| 2 | Sori on adjacent veins opening towards each other, a raised line remaining between the sori when they are ripe |
| 2' | Sori all facing the same way except in a few species which have simple fronds and then the raised line between adjacent sori lacking |
