FILMY FERNS  , a

general name for a group of ferns with delicate much-divided leaves and often moss-like growth, belonging to the genera Hymenophyllum, Todea and Trichomanes . They require to be kept in close cases in a cool fernery, and the stones and moss amongst which they are grown must be kept continually moist so that the evaporated water condenses on the very numerous divisions of the leaves .