There are an estimated 15,000 species of ferns that exist at the present time, all of which have true roots, complex leaves and stems. The stem from which the fern leaves, or fronds, protrude is known as a rhizome. Often difficult to see because of the surrounding foliage, rhizomes sometimes exist entirely underground. Rhizomes contain both the conducting materials xylem and phloem, which transport water and nutrients, and a strengthening tissue known as sclerenchyma fiber. The Native Americans frequently utilized fern rhizomes for domestic purposes, beating out the starch for consumption and using the fiber as a textile.