fern

Plant of the class Filicineae, related to gymnosperms and angiosperms; however, ferns reproduce by spores and not seed. Most are perennial, spreading by low-growing roots. The leaves, known as fronds, vary widely in size and shape. Some taller types, such as tree-ferns, grow in the tropics. There are over 7,000 species.

Common forms include polypody (Polypodium); shield fern (Polystichum); maidenhair (Adiantum capillus-veneris); and bracken (Pteridium), a common weed.