Fern

fern, (class Polypodiopsida), class of nonflowering, herbaceous vascular plants that possess true roots, stems, and complex leaves and that reproduce by spores. The number of known extant fern species is about 10,500, but estimates have ranged as high as 15,000, the number varying because certain groups are as yet poorly studied and because new species are still being found in unexplored tropical areas. The ferns constitute an ancient division of vascular plants, some of them as old as the Carboniferous Period (beginning about 358.9 million years ago) and perhaps older. Their type of life cycle, dependent upon spores for dispersal, long preceded the seed-plant life cycle. Another informal name for the group, monilophytes, has gained currency in modern botanical literature.