| 1 | Lamina pinnate, with mostly free lobes, at most the upper 1 or 2 pairs adnate |
| 1' | Lamina simple or variously divided, the lobes all adnate or connected along the rachis |
| 2 | Lobes 7-20 on each side of the rachis, scales circular or elliptic, often with eroded margins, sori in a single row between costa and margin |
| 2' | Lobes 4 or 5 on each side of the rachis, scales (narrowly) ovate or triangular, sori scattered over the lamina |
| 3 | Sori deeply sunken, visible as protrusions on the upper surface |
| 3' | Sori superficial or slightly immersed |
| 4 | Longest lobes 0.3-0.5 cm wide, scales 0.2-0.3 mm wide, sorus close to the margin |
| 4' | Longest lobes 0.7-7 cm wide, scales 0.5-3.5 mm wide, sori generally close to the costa, at most halfway to the margin |
| 5 | Rhizome not white waxy, with scattered sclerenchyma strands or with sclerified circumvascular sheaths, scales pseudopeltate |
| 5' | Rhizome white waxy, with both scattered sclerenchyma strands and sclerified circumvascular sheaths, scales peltate |
| 6 | Lamina margin entire, rhizome dorsiventrally flattened, with only sclerified circumvascular sheaths, lamina herbaceous, apex of lobes rounded or acute. |
| 6' | Lamina margin undulate, rhizome more or less terete, with only scattered sclerenchyma strands, lamina membranaceous, apex of lobes long-acuminate. |
| 7 | Scales 2-7 mm long, cells elongated, lamina herbaceous |
| 7' | Scales 0.5-1.3 mm long, cells more or less isodiametric, lamina thin-herbaceous or membranaceous |
| 8 | Sori more or less regularly spaced, either in a single row (sometimes irregular-ly doubled) between costa and margin, or in two rows between the lateral veins. |
| 8' | Sori irregularly scattered over the lamina |
| 9 | Lamina pinnatifid, or pinnate near base |
| 9' | Lamina simple, rarely irregularly lobed |
| 10 | Scales round or elliptic, the margin entire, often with eroded margins, roots densely set, lamina base narrowly angustate, the stipe winged for a considerable part |
| 10' | Scales narrowly ovate or triangular, margin denticulate, roots sparsely set, lamina base cuneate-angustate or cuneate, stipe not winged |
| 11 | Lamina pinnatifid throughout, the rhizome without sclerified circumvascular sheaths, lamina index 1.5-2, connecting veins 2-4, sori 1.6-3 mm diam. |
| 11' | Lamina pinnate in basal part, rhizome with sclerified circumvascular sheaths, lamina index 1.3, connecting veins 7, sori 1 mm diam. |
| 12 | Scales peltate, appressed or slightly spreading, lamina with 2-16 pairs of lobes. |
| 12' | Scales pseudopeltate or basifixed, distinctly spreading, lamina with 15-33 pairs of lobes |
| 13 | Scales round or elliptic, often with eroded margins, peltate |
| 13' | Scales (narrowly) ovate or triangular, pseudopeltate |
| 14 | Lamina elliptic, index 2.5-5, base cuneate-angustate, scales 0.8-1.2 mm long. |
| 14' | Lamina linear, index 10-20, base narrowly angustate, decurrent into a long wing, scales 1.5-2.5 mm long |
| 15 | Sori in several rows between midrib and margin, in two (irregular) rows between each pair of veins, connecting veins catadromous or sometimes anadromous |
| 15' | Sori in a single (sometimes irregularly doubled) row between costa and margin, connecting veins anadromous |
| 16 | Roots densely set, rhizome terete, sclerenchyma strands 50-110, sori 1 (or 2) per veinlet |
| 16' | Roots sparsely set, the rhizome dorsiventrally flattened, sclerenchyma strands 0-15, sori 2-4 per veinlet |
| 17 | Lamina base narrowly angustate, decurrent into a long wing, roots sparsely set, scales glabrous, veins more or less immersed and vague. — Peninsular Malaysia. |
| 17' | Lamina base truncate-angustate or cuneate-angustate, roots densely set, scales bearing multiseptate hairs at least when young, veins prominent and distinct. — Philippines |
| 18 | Connecting veins forming one row of large areoles parallel to the costa, bordered by several smaller areoles; costal areole, if present, bordered by included veins |
| 18' | Connecting veins forming a row of more or less equally sized areoles between adjacent veins, costal areole, if present, bordered by the connecting veins |
| 19 | Rhizome without sclerenchyma or circumvascular sheaths |
| 19' | Rhizome with only circumvascular sheaths |
| 20 | Lamina pinnatifid, or bipinnatifid |
| 20' | Lamina simple |
| 21 | Longest lobes of lamina 5-6 cm wide, widest at or above middle; lamina undersurface with acicular hairs, smaller veins prominent and distinct. |
| 21' | Longest lobes of lamina 0.5-2.5 cm wide, widest below middle; lamina undersurface without acicular hairs, smaller veins more or less immersed and indistinct |
| 22 | Lamina widest below the middle, thin-herbaceous, apical lobe always longer than upper lateral lobes, veins prominent and distinct. — New Guinea. |
| 22' | Lamina widest above the middle, herbaceous or subcoriaceous, the apical lobe shorter or longer than upper lateral lobes, veins more or less immersed and indistinct. — Philippines |
| 23 | Lamina undersurface without acicular hairs |
| 23' | Lamina undersurface with acicular hairs |
| 24 | Smaller veins more or less immersed and indistinct, roots sparsely set, scales densely set, scales clathrate or subclathrate, lamina thin-herbaceous. |
| 24' | Smaller veins prominent and distinct, roots densely set, scales apically densely set, elsewhere more sparsely set, clathrate except for the hyaline marginal region, lamina herbaceous |
| 25 | Veins immersed and distinct, phyllopodia obscure, lamina herbaceous, or subcoriaceous, base truncate, stipe not or shortly winged |
| 25' | Veins prominent and distinct, phyllopodia more or less distinct, lamina thin-her-baceous, base narrowly angustate, the stipe winged for a considerable part. |
| 26 | Rhizome white waxy underneath the scales, without sclerified circumvascular sheaths, sclerenchyma strands always present, scattered |
| 26' | Rhizome not white waxy underneath the scales, with sclerified circumvascular sheaths, sclerenchyma strands absent or present |
| 27 | Rhizome with scattered strands of sclerenchyma |
| 27' | Rhizome with sclerenchyma strands situated dorsally of the vascular cylinder. |
| 28 | Sori predominantly on connective veins, roots sparsely set, veins zigzag. |
| 28' | Sori mostly irregularly scattered on the smallest veinlets, roots densely set, veins more or less straight |
| 29 | Rhizome with 50-100 sclerenchyma strands, phyllopodia 1.5-6 cm apart, scales densely set, slightly to distinctly spreading; lamina herbaceous. |
| 29' | Rhizome with 8-15 sclerenchyma strands, phyllopodia 0.2-1.1 cm apart, scales apically densely set, elsewhere more sparsely set, appressed; lamina thin-herbaceous |
| 30 | Sori predominantly on connective veins |
| 30' | Sori mostly irregularly scattered on the smallest veinlets |
| 31 | Rhizome bearing scales and hairs, roots sparsely set, scales densely set; connecting veins catadromous, lamina herbaceous or subcoriaceous. |
| 31' | Rhizome bearing only scales, roots densely set, scales apically densely set, elsewhere more sparsely set; connecting veins anadromous (rarely catadromous), lamina thin-herbaceous |
| 32 | Scales peltate |
| 32' | Scales pseudopeltate |
| 33 | Connecting veins anadromous (rarely catadromous), lamina thin-herbaceous. |
| 33' | Connecting veins catadromous, lamina herbaceous |
| 34 | Lamina 10-30 cm long; rhizome with 9-10 vascular bundles, roots sparsely set; scales densely set, distinctly spreading, denticulate; phyllopodia more or less distinct; stipe 0.5-1.5 mm thick, lamina base narrowly angustate, decurrent to a long wing, margin sinuate, veins more or less immersed and indistinct. |
| 34' | Lamina 65-85 cm long; rhizome with 16-21 vascular bundles, roots densely set; scales apically densely, elsewhere more sparsely set, slightly spreading, dentate; phyllopodia obscure, stipe 3.5-7 mm thick, lamina base truncate or cu-neate, margin entire, veins prominent and distinct |
