| 1 | Petiole and rachises abaxially keeled |
| 1' | Petiole and rachises abaxially bi-angular, rarely only obscurely so. |
| 2 | Basal (primary) pinnae strongly reduced (Fig. 25) |
| 2' | Basal pinnae hardly or not reduced. |
| 3 | Pinnules incised beyond ¾ of their width, with capillary segments 0.2-0.4 mm wide, wider at the sorus, the wing connecting them as wide (Fig. 28); sori uninerval. |
| 3' | Pinnules at the base incised beyond the middle, the segments not capillary, 0.3-0.8(-1) mm wide, connected by a wing of ½-1 mm; sori very predominantly uninerval. |
| 3'' | Pinnules at the base not incised to the middle, the segments 0.8 mm wide or more; sori usually on more than one vein (except in L. tetragona). |
| 4 | Outer incisions of the pinnules reaching to the middle; lobes longer than broad. |
| 4' | No incisions reaching beyond 1/4 of the width of the pinnules; lobes broader than long. |
| 5 | Sori uni- or binerval; largest pinnules 10-12 mm long |
| 5' | Sori bi- or trinerval; largest pinnules 7-8 mm long |
| 6 | Veins 1 mm apart |
| 6' | Veins 0.5 mm or less apart |
