The one fern I grow on purpose. Others come in as spores on the orchid bark and start growing in the orchid pots--rabbit's foot fern, Boston fern-- but this one's deliberate.
Pic two is the underside of a female leaf, showing spores at the tips. For the longest time I thought this was developing fungus, and I sprayed and sprayed.... You can shake these down over an upside-down clay pot set in a saucer of water so it stays damp, and they'll sprout.