KEY TO THE VARIETIES

1Fertile fronds isomorphous with sterile ones, or nearly so, their lower surface glabrous be tween veins
1'Fertile fronds much contracted, their lower surface bearing many hairs between veins
2Indusia distinct on all sori
2'Indusia very small, hidden by sporangia, or lacking
3Costae densely short-hairy on upper surface
3'Costae glabrous on upper surface