| 1 | Sori scattered on the lamina |
| 1' | Sori in a single row parallel to the costa or between two veins |
| 2 | Rhizome without sclerified circumvascular sheaths, with scattered strands of sclerenchyma, white waxy underneath the scales |
| 2' | Rhizome with sclerified circumvascular sheaths, or without any sclerification, not white waxy underneath the scales |
| 3 | Rhizome without any sclerification, venation with one row of large areoles parallel to the costa, costal areole, if present, formed by smaller veins. |
| 3' | Rhizome with circumvascular sheaths; venation with several equally sized areoles, costal areole, if present, bordered by the first connecting vein |
| 4 | Roots sparsely set, scales densely set |
| 4' | Roots densely set, scales apically densely set, elsewhere more sparsely set |
| 5 | Rhizome with circumvascular sheaths and scattered strands of sclerenchyma, sori on the whole surface of the lamina |
| 5' | Rhizome with only circumvascular sheaths, sori absent from the basal parts of the lamina |
| 6 | Scales in central region glabrous, margin entire or denticulate, phyllopodia more or less distinct, lamina thin-herbaceous, base narrowly angustate, decurrent to a long wing, connecting veins 1-3, between midrib and margin, mainly anadromous |
| 6' | Scales in central region bearing hairs at least when young, margin dentate, phyllopodia not elevated, lamina herbaceous, base truncate or cuneate, connecting veins 4-7 between midrib and margin, catadromous |
| 7 | Lamina pinnate |
| 7' | Lamina simple or pinnatifid |
| 8 | Sori deeply sunken, visible as protrusions on the upper surface |
| 8' | Sori superficial or slightly immersed |
| 9 | Rhizome white waxy, with sclerified circumvascular sheaths and scattered sclerenchyma strands, scales peltate, 0.6-1.4 mm wide |
| 9' | Rhizome not white waxy, with only scattered sclerenchyma strands, scales pseudopeltate, 2.5-3.5 mm wide |
| 10 | Scales circular or elliptic, peltate, often with eroded margins |
| 10' | Scales (narrowly) ovate or triangular, pseudopeltate, margins usually intact |
| 11 | Lamina elliptic, base cuneate-angustate, not long-decurrent, scales 0.8-1.2 mm long |
| 11' | Lamina linear, base narrowly angustate, decurrent into a long wing, scales 1.5-2.5 mm long |
| 12 | Sori more or less in one row parallel to the costa, veins dichotomously branched below the middle |
| 12' | Sori in two (irregular) rows between each pair of veins, the veins dichotomously branched near the margin |
| 13 | Roots densely set, rhizome more or less terete, sclerenchyma strands 50-110, sori 1 (or 2) per veinlet |
| 13' | Roots sparsely set, rhizome dorsiventrally flattened, sclerenchyma strands 0-15, sori 2-4 per veinlet |
