More than 10,000 species of fern have been scientifically catalogued, some of which date back 360 million years ago to the Carboniferous period. Man has utilized the plants in various ways since he first began to walk on the Earth. Ferns, or parts of the ferns, have been used as a food source, as bedding and stuffing for cushions, as medicinal treatments, as material for roof thatching, and as ornamentals. Most recently, ferns have acted as a subject of study in biological research, scientists being extremely interested in their retainment of a primitive lifecycle that involves two separate, generally independent generations.