Maidenhair ferns, Adiantum, is a fairly large genus in the family Pteridaceae.  They are very dainty ferns, often with black stalks and thin, light green foliage. They prefer humus rich, moist soil, and often grow in rock crevices where water trickles down. One species, the delta maidenhair fern (A. raddianum) is a popular houseplant. Most species are native to the Andes mountains and eastern Asia.