| 1 | Rhizome short-creeping with fronds close together; epiphytes or rock-plants, not high-climbing. |
| 1' | Rhizome high-climbing. |
| 2 | Fronds always simple; stipes jointed to phyllopodia; veins free except near margin; usually epiphytes. |
| 2' | Fronds usually pinnate (if simple, veins much anastomosing); stipes not jointed to rhizome; usually rock-plants. |
| 3 | Veins free |
| 3' | Veins anastomosing |
| 4 | Veins free. |
| 4' | Veins anastomosing |
| 5 | Pinnate or bipinnate, all pinnae and pinnules jointed at base (except on some bathyphylls). |
| 5' | Pinnate; terminal leaflet not jointed at base. |
| 6 | Fronds of high-climbing part of plant simply pinnate (bathyphylls sometimes bipinnate); only two rows of fronds on rhizome (two meristeles in internodes). |
| 6' | Fronds of high-climbing part of plant usually bipinnate; more than two rows of fronds on mature rhizome (more than two meristeles in internodes) |
| 7 | Fertile pinnae fully acrostichoid |
| 7' | Fertile pinnae bearing separate exindusiate sori on small lobes at ends of veins. |
