| 1 | Caudex long-creeping with well-spaced fronds. |
| 1' | Caudex short-creeping, fronds close together. |
| 2 | Pinnae one pair, opposite, always asymmetric |
| 2' | Pinnae 2-6 pairs, distal ones small and adnate, rest with variable asymmetry |
| 3 | Pinnae all narrowly cuneate at base, fertile ones commonly 1 cm wide; hooked hairs lacking on lamina and sporangia |
| 3' | Pinnae not all narrowly cuneate at base, fertile ones always much more than 1 cm wide; hooked hairs present on some parts of lamina and usually on sporangia. |
| 4 | Pinnae 1-3 pairs; no buds at their bases. |
| 4' | Pinnae of well-grown plants more than 3 pairs; a bud always present at base of uppermost pinna. |
| 5 | Pinnae always opposite; fertile pinnae with undulate margins; hooked hairs present on basal scales and on sporangia |
| 5' | Pinnae not always opposite; fertile pinnae sharply serrate-crenate distally; no hooked hairs on scales nor on sporangia |
| 6 | Bud confined to base of uppermost pinna; pinnae widest in basal half; hydathodes on upper surface conspicuous |
| 6' | Buds present at bases of several pinnae; pinnae usually widest above middle; hydathodes not conspicuous 57. P. ramosii |
| 7 | Hooked hairs present on sporangia |
| 7' | Hooked hairs lacking on sporangia |
