| 1 | Pinnae of fronds of adult plants about equal in size to apical lamina. |
| 1' | Apical lamina much larger than pinnae, or fronds simple. |
| 2 | Glands present on lower surface of pinnae |
| 2' | Glands lacking on lower surface of pinnae. |
| 3 | Pinnae 2-3 pairs; glands present on indusia or sporangia or both |
| 3' | Pinnae to at least 7 pairs; no glands on indusia and sporangia. |
| 4 | Pinnae to 30 x 5 cm; spores with a median wing and cross-wings |
| 4' | Pinnae to 15 x 2.5 cm; spores with many separate small wings. |
| 5 | Sori exindusiate; glands usually lacking on lower surface between veins. |
| 5' | Sori indusiate; glands always present on lower surface between veins. |
| 6 | No free pinnae; sometimes one small pair broadly adnate |
| 6' | Free pinnae present on adult plants. |
| 7 | Sporangia bearing glands near annulus. |
| 7' | Sporangia bearing setae, not glands, near annulus. |
| 8 | Apical lamina to 20 x 3.5 cm; midrib of apical lamina and rachis glabrous on lower surface |
| 8' | Apical lamina to 6x1.7 cm; hairs present on lower surface of midrib of apical lamina and rachis |
| 9 | Terminal lamina lobed ¼-⅓ towards midrib; pinnae to at least 1 cm long. |
| 9' | Terminal lamina crenate; pinnae 2-5 mm long |
| 10 | Pinnae 4-8 cm long |
| 10' | Pinnae not over 2 cm long. |
| 11 | No glands on lower surface |
| 11' | Glands present on lower surface |
| 12 | Veins in basal part of apical lamina forked, their branches anastomosing. |
| 12' | Veins in apical lamina not forked |
| 13 | Apical lamina widest near its base; pinnae 1 pair |
| 13' | Apical lamina not widest near its base; pinnae 3 pairs, decreasing downwards |
