| 1 | Sori not acrostichoid, or if apparently so, a thin indusium present all along edge of fertile leaflets. |
| 1' | Sori acrostichoid (no thin reflexed indusium on fertile leaflets) |
| 2 | Sori continuous along each side of the costa of a leaflet, a sterile lamina present beyond the sorus or not |
| 2' | Sori not continuous throughout length of a leaflet; one sorus to each areole along the costa. |
| 3 | Small ferns, simply pinnate; edges of pinnae sharply toothed |
| 3' | Large ferns, at least bipinnatifid; edges of pinnae not sharply toothed. |
