| 1 | Frond very small, with one vein only; sorus near apex, along the vein. |
| 1' | Frond with lateral veins as well as a main vein. |
| 2 | Frond linear, sori one or more, on separate free branches, which run close to and parallel with main vein |
| 2' | Fronds otherwise; veins anastomosing at least near the margin. |
| 3 | Sori linear, in marginal grooves or superficial and parallel to margin; veins forming one series of areoles, anastomosing only near the margin |
| 3' | Sori along veins, variously disposed; veins anastomosing copiously throughout the lamina. |
