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Mortimer Abramowitz Gallery of PhotomicrographyFern Stalk Longitudinal SectionSpore-producing plants belonging to the division Filicophyta are commonly referred to as ferns. The primitive vascular plants are extremely diverse and have been present on Earth for over 300 million years.
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. Most ferns proliferate through an alternation of generations, switching between sexual and asexual forms. The sexual form is difficult to find in nature and the asexual form, known as a sporophyte, is the fern that is commonly known. Sporophyte ferns are able to reproduce in two different asexual manners. Vegetative cloning occurs when a rhizome branches and splits, often forming sizeable colonies that are genetically consistent throughout. The alternate form of asexual reproduction occurs when spores, which are usually encased in sporangia on the undersides of leaves, break out and land in a place suitable for germination. |
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