| 1 | Rhizome bristly or hairy, stipes not jointed to it; terrestrial. |
| 1' | Rhizome scaly, stipes usually jointed to it; mostly epiphytes. |
| 2 | Fronds dimorphous; fertile fronds narrow, acrostichoid |
| 2' | Fronds uniform; sori small and round |
| 3 | Young sori protected by umbrella-shaped paraphyses. |
| 3' | Young sori not so protected. |
| 4 | Sporangia acrostichoid on a constricted apical part of the frond |
| 4' | Sporangia in separate sori, or whole fertile frond narrow and acrostichoid. |
| 5 | Sori somewhat elongate, close to and parallel with edge of lamina. |
| 5' | Sori otherwise. |
| 6 | Fronds small, fertile ones (or fertile parts) contracted |
| 6' | Fronds larger, not dimorphous |
| 7 | Fronds bearing stellate hairs. |
| 7' | Fronds not bearing stellate hairs. |
| 8 | Fronds simple, entire. |
| 8' | Fronds branched dichotomously, sporangia acrostichoid on part of surface of fertile frond. |
| 9 | Sori continuous along margin of narrow fertile frond or between margin and midrib. |
| 9' | Sori separate, round, variously distributed |
| 10 | Sori at the ends of free veins (veins conspicuous). |
| 10' | Sori not at ends of free veins (veins often inconspicuous). |
| 11 | All veins free |
| 11' | Some veins anastomosing |
| 12 | Veins anastomosing to form only one series of areoles along costae. |
| 12' | Veins more copiously anastomosing. |
| 13 | Rhizome swollen and ant-inhabited. |
| 13' | Rhizome not ant-inhabited. |
| 14 | Rhizome not scaly; sori on distinct small lobes |
| 14' | Rhizome copiously scaly; sori not on distinct lobes |
| 15 | Fertile fronds (or fertile parts) acrostichoid, usually much reduced as compared with sterile. |
| 15' | Fertile fronds (or fertile parts) not acrostichoid. |
| 16 | Fronds pinnate or pinnatifid, lower pinnae or lobes always sterile. |
| 16' | Fertile fronds wholly fertile. |
| 17 | Fronds pinnate, sterile pinnae jointed to rachis |
| 17' | Fronds pinnatifid |
| 18 | Fronds strongly trilobed |
| 18' | Fronds simple. |
| 19 | Fronds thin, all veins visible. |
| 19' | Fronds coriaceous, at most main veins visible. |
| 20 | Fronds c. 10 cm long; terrestrial |
| 20' | Fronds c. 30 cm long; rock-plants or epiphytes |
| 21 | Sterile fronds narrow |
| 21' | Sterile fronds circular to broadly lanceolate. |
| 22 | Sterile fronds circular |
| 22' | Sterile fronds longer than wide, apex acute |
| 23 | Fronds pinnate or pinnatifid, pinnae or segments jointed to rachis. |
| 23' | Fronds simple or pinnatifid, segments not jointed to rachis. |
| 24 | Separate short humus-collecting fronds present |
| 24' | Separate humus-collecting fronds lacking. |
| 25 | Bases of fronds broad, humus-collecting. |
| 25' | Bases of fronds not humus-collecting. |
| 26 | Fronds on special branches of rhizome |
| 26' | Fronds not on special branches |
| 27 | Fronds dimorphous |
| 27' | Fronds not dimorphous |
| 28 | Separate humus-collecting fronds present |
| 28' | Separate humus-collecting fronds lacking. |
| 29 | Sori elongate, oblique, parallel to main lateral veins. |
| 29' | Sori otherwise. |
| 30 | Fronds thin, all veins visible |
| 30' | Fronds fleshy or leathery, at most main veins visible. |
| 31 | Main lateral veins distinct; scales not clathrate |
| 31' | Main lateral veins not distinct; scales clathrate |
| 32 | Sori elongate, near margins of thin frond |
| 32' | Sori otherwise. |
| 33 | Fronds very narrow, not dimorphous; sori elongate, close to costa. |
| 33' | Fronds otherwise; sori round. |
| 34 | Fronds always coriaceous; edges usually notched; scales not clathrate. |
| 34' | Fronds not always coriaceous; edges not notched; scales clathrate |
