| 1 | Sterile pinnae very coriaceous, drying brownish; fertile pinnae 10-20 mm wide; spores 90-110 μm long excluding perispore. |
| 1' | Sterile pinnae not very coriaceous, drying dark olive-green; fertile pinnae rarely to 10 mm wide; spores c. 45-65 μm long excluding perispore. |
| 2 | Stalks of largest pinnae 5-20 mm long; apices of sterile pinnae rather abruptly short-acuminate; veins in sterile pinnae widely spaced and at c. 60° to costa |
| 2' | Stalks of lowest pinnae always short; apices of sterile pinnae gradually attenuate; veins of sterile pinnae less conspicuous, closer, at their bases almost at right angles to costa |
| 3 | Upper surface of fertile pinnae not over 2 mm wide; wing of spore narrow, lacking reticulate thickening |
| 3' | Upper surface of fertile pinnae wider; wing of spore otherwise. |
| 4 | Sterile pinnae 3-5 cm wide, on young plants at least abruptly contracted to a short-acuminate apex; spores with ample folded perispore |
| 4' | Sterile pinnae less than 3 cm wide (usually less than 2 cm), apex always gradually attenuate; spores bearing a perispore of many small wings |
