| 1 | Veins free or with irregular slight anastomosis |
| 1' | Veins anastomosing in sterile fronds |
| 2 | Pinnae c. 3 cm long; veins 3 or 4 pairs, nearly all simple |
| 2' | Pinnae much longer; veins 6 or more pairs, mostly forked |
| 3 | Sori indusiate |
| 3' | Sori exindusiate |
| 4 | Hairs between veins scattered all over upper surface |
| 4' | Hairs between veins on upper surface present only near sinuses and margins of pinna-lobes |
| 5 | Pinna-lobes at most crenate |
| 5' | Pinna-lobes, except those of distal pinnae, distinctly lobulate. |
| 6 | Lamina of largest fronds 30-40 cm long; suprabasal fertile pinnae to 12 × 2.5 cm |
| 6' | Lamina of largest fronds 50-75 cm long; suprabasal fertile pinnae to 15 cm or more long, 2.5-4 cm wide |
| 7 | Stipes rusty brown, not glossy |
| 7' | Stipes nearly black, glossy |
| 8 | Fertile pinnae not greatly contracted; most sori separate |
| 8' | Fertile pinnae with lobes much contracted |
| 9 | Young fertile fronds with distinctly separate sori |
| 9' | Young fertile fronds with sporangia running along all veins and at maturity covering lower surface of pinna-lobes |
| 10 | Young sori round, indusiate, on pinna-lobes 1.5-2.5 mm wide, completely cover ing lobes when mature |
| 10' | Young sori of varied form; if indusiate on much wider pinna-lobes which they do not cover when mature |
| 11 | Sori all irregularly elongate along veins, exindusiate |
| 11' | Sori all round to elliptic, not linear, indusiate or not |
| 12 | Suprabasal pinnae of mature plants to 13 × 2.5 cm, lacking costular aréoles; no buds on upper surface of sterile fronds. |
| 12' | Suprabasal fertile pinnae of mature plants to 25 × 5 cm; several pairs of costular aréoles present; buds present on upper surface of some costae of sterile fronds near the rachis |
| 13 | Sori in one row on each side of costules of pinna-lobes |
| 13' | Sori on each side of veins which run to crenatures on margins of pinna-lobes |
| 14 | Basal pinnae of fertile fronds bearing 1 pair of free pinnules and 2 or 3 pairs adnate |
| 14' | Basal pinnae of fertile fronds lacking pinnules |
| 15 | Fronds to 70 cm long; sterile pinnae to 21 × 4 cm. |
| 15' | Fronds to 30 cm long; sterile pinnae much smaller |
