Made from plants that produce fibrous products based on polymers of the cellulose molecule. Cotton plants produce separate cellulose fibers, whereas wood pulp is made by mechanically and/or chemically separating wood fibers. Other sources of cellulose are fibers such as flax manila, ramie and jute.
Rayon is made by dissolving wood pulp in a solution and extruding that solution through spinnerets into a chemical bath that regenerates the fibers.
References for this information:
Smart Clothes and Wearable Technology, 2009, Pages156-182