| 1 | Sporangia borne on, and (almost) confined to, a longitudinal vein on either side of the costa/costule and parallel to it, rarely spreading onto the indusium, or borne on vein arches flanking the costa/costules; indusium at least initially present |
| 1' | Sporangia not confined to such a vein or arch (except in incompletely fertile leaves of Brainea); indusium none |
| 2 | Veins free, except for the para costal commissure of fertile leaves bearing the sorus; or a submarginal commissure rarely present; sterile parts without the paracostal commissure. Leaves simple, pinnatifid, or simply pinnate, or, if bipinnate (rare), the rhachis erect; veins of sterile parts quite free |
| 2' | Veins anastomosing beside the paracostal commissure or vein arch bearing the sori; or this commissure present in sterile as well as in fertile leaves |
| 3 | Lamina deeply pinnatifid to once pinnate, mostly tapering at the base; veins forming 1-3 series of areoles |
| 3' | Lamina pinnate and pinnatifid (or almost bipinnate at base) or, if simply pinnate or simple, with very amply anastomosing veins; lamina base various. Lamina hardly or not dimorphic |
| 4 | Pinnae articulate sporangia with acrostichoid arrangement; stem scandent |
| 4' | Pinnae non-articulate; sporangia (in fully fertile leaves) following the veins, eventually often seemingly acrostichoid; stem erect, rather trunk-like |
