This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Fronds simple or compound, circinate in vernation. In-dusium marginal, or dorsal, or absent. Spore-cases small, usually stalked, not on an elevated receptacle, partially or wholly surrounded with a vertical elastic ring bursting transversely.