This name has been applied to various species belonging to the genera Hymenophyllum, Todea, and Trichomanes. Owing to the peculiar atmospheric conditions necessary for their successful culture, Filmy Ferns are not a very marketable commodity. They are wonderfully beautiful and elegant in appearance, the fronds in many cases resembling the more delicate and more finely divided kinds of green seaweeds. Most of them must be grown in close cases in a cool atmosphere that is always highly charged with moisture. They are planted in a mixture of fibrous peat and loam to which some sphagnum moss and a little broken charcoal are added; and they are usually planted in a kind of rockery made of pieces of rock. Several kinds, however, do well when tied to pieces of tree-fern stem or blocks of peat, more especially those having more or less creeping rhizomes. Water is best applied carefully to the rocks or pieces of stem on which the plants are growing, and the fronds may be "dewed" occasionally with a fine spray from the syringe. The best-known kinds of Filmy Ferns are Hymenophyllum tunbridgense, Trichomanes radicans, (the Killarney Fern), and Todea superba (fig. 317).

Todea superba.

Fig. 317. - Todea superba.