Prepared Microscope Slides: Stained Cotton Stem Cross Section
While most types of cells are so tiny that a microscope is needed to observe them, cotton fibers are easily visible to the naked eye, reaching lengths of up to 2 inches (50mm). In fact, the fibers from cotton can be the longest cells of any plant. But the equally fascinating cotton stem cells require observations with a microscope at 40X or higher. The cells within the stem are of varying sizes and are arranged in distinct boundaries that form a symmetry.
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. Under natural conditions, the cotton bolls will tend to increase the dispersion of the seeds.
The plant is a shrub native to tropical and subtropical regions around the world, including the Americas, Africa, and India. The greatest diversity of wild cotton species is found in Mexico, followed by Australia and Africa. Cotton was independently domesticated in the Old and new Worlds. The English name derives from the Arabic (al) qutn قُطْن, which began to be used circa 1400 AD. The Spanish word, "algodón", is likewise derived from the Arabic.
The fiber is most often spun into yarn or thread and used to make a soft, breathable textile. The use of cotton for fabric is known to date to prehistoric times; fragments of cotton fabric dated from 5000 BC have been excavated in Mexico and the Indus Valley Civilization (modern day Pakistan). Although cultivated since antiquity, it was the invention of the cotton gin that so lowered the cost of production that led to its widespread use, and it is the most widely used natural fiber cloth in clothing today.