With the exception of synthetic polymers, most economically important products, such as paper, cordage (cords and rope) and textiles, are derived from plant fibers. Fibers are elongate cells with tapering ends and very thick, heavily lignified cell walls. Fiber cells are dead at maturity and function as support tissue in plant stems and roots. The lumen or cavity inside mature, dead fiber cells is very small when viewed in cross section. Fibers are one of the components of sclerenchyma tissue, along with shorter, thick-walled sclereids (stone cells) which produce the hard tissue of peach pits and the gritty texture in pears. Fibers are also associated with the xylem and phloem tissue of monocot and dicot stems and roots, but generally not in the wood of gymnosperms. In fact, the primary reason why gymnosperm woods are generally softer and lighter than angiosperm woods is the presence in angiosperm wood of dense clusters of heavily-lignified, thick-walled fiber cells. The densely-packed fiber cells greatly increase the hardness and density of angiosperm woods.

Longitudinal section and cross section of a fiber cell.

Fibers are also the basic component of wood products, such as paper. One of the earliest records for making sheets of paper dates back at least 5500 years ago to the ancient Egyptians who pressed together thin strips of papyrus stems (Cyperus papyrus) to write on. Egyptian papyrus belongs to the sedge family (Cyperaceae). The inner pith of the stems was cut into strips after removing the outer epidermal layer. The strips were then laid side-by-side and over one another at right angles to form two overlapping layers, one vertical and one horizontal. This "sheet" was pounded to release a glucose-rich sap which served as a bonding agent. The sheets were hammered to make them more compact and rubbed with a stone or bone to produce a smooth surface. This process is similar to bark paper discussed below. To make a scroll, several of these flat sheets were pressed and bonded together.

Another ancient writing material developed in Europe: Parchment is a writing material made from specially prepared untanned skins of animals—primarily sheep, calves, and goats. It has been used as a writing medium for over two millennia. It is also called animal membrane by libraries and museums. It was very durable and could be folded and stiched together to make pages of a book. A thick book containing hundreds of pages required hundreds of animals and was very expensive. According to Wikipedia, the term parchment is often used in non-technical contexts to refer to any animal skin, particularly goat, sheep or cow, that has been scraped or dried under tension. The term originally referred only to the skin of sheep and, occasionally, goats. The equivalent material made from calfskin, which was of finer quality, was known as vellum (from the Old French velin or vellin, and ultimately from the Latin vitulus, meaning a calf).

Any discussion of natural paperlike products made from wood pulp or fiber cells should include paper wasps of the yellow jacket family (Vespidae). Some of the earliest paper makers on earth were undoubtedly wasps of the genera Polistes and Vespula. The nest of a paper wasp (Polistes fuscatus) is formed by mixing saliva with fibers rasped from dead wood until a pulp similar to papier-mâché is formed. Yellow jackets (Vespula) also build a nest made of this papier-mâché material. Some species of Vespula are also referred to as hornets. The umbrella-shaped nests of paper wasps are attached by a short stalk to the underside of overhanging surfaces such as the eaves of a house or under bridges. The nests contain a single layer of six-sided chambers or cells that fit neatly together like the cells of a honeycomb. Chambers in the nest contain wasp larvae which are fed caterpillars collected by adult female workers. These wasps are easily provoked and can sting forcibly and repeatedly, as this author can testify. This is especially true of yellow jacket nests. If you find small nests made of a mudlike material on the eaves of your house, they probably are from the mud dauber wasp (Sceliphron caementarium) of the family Sphecidae.

Rice paper, another ancient paper from the Orient, was made originally from the pith of the rice paper plant (Tetrapanax papyriferus), a member of the aralia family (Araliaceae). This species is listed in some references (such as your textbook) as Fatsia papyrifera. It is not made from the rice plant (Oryza sativa). Rice paper is utilized to this day as a medium for painting and in the manufacture of imitation flowers; however, today's paper labeled as "rice paper" is made from a meshwork of pressed fibers from the pulp of bamboo, paper mulberry (Broussonetia papyrifera) or another species. It is commonly used in calligraphy and ink paintings. In the case of authentic rice paper, stems of Tetrapanax papyriferus are soaked in water to loosen the pith which is removed and dried. Thin sheets are shaved (peeled) from the pith cylinder, like a veneer is shaved off a tree trunk. The sheets are then cut into various sizes and pressed lightly to flatten. Sheets of pith paper were once used in watercolor and gouache paintings, but have largely been replaced by other types of paper made from pulp. Contrary to some botany texts, the pith was not pounded to make authentic rice paper from Tetrapanax papyriferus.

Before the Spanish conquest, the Aztecs used fig bark to make a kind of paper. In fact, the common Spanish name for many species of Ficus is "amate," from the Nahuatl word "amatl" meaning paper. Both Aztecs and Mayans used bark from native fig trees to make paper for the original Mexican codices. Bark was stripped from the fig tree, soaked in water, washed, boiled and split into thin strips. The strips were then placed on a plank and pounded with a stone until a sheet of paper was formed, a process not unlike the production of papyrus paper by the ancient Egyptians.

Mexican bark paper is still being made to this day, particularly in the state of Puebla. The process is summarized by Anna Lewington in Plants For People (Oxford University Press, 1990). The fibrous inner phloem fibers are separated from the outer bark in strips and boiled for several hours in water containing lime. This procedure softens the fibers and makes them separate more easily. After rinsing, the strips are arranged in a grid pattern on a smooth board and then beaten with a flattened stone until the fibers mesh together. The sheets are left on the boards and allowed to dry in the sun. According to Lewington (1990), the bark of several tree species are used, including Ficus tecolutensis and Morus celtidifolia of the mulberry family (Moraceae) and Trema micrantha of the elm family (Ulmaceae).

A process similar to that of bark paper can also be used as a substitute for cloth. The best known bark cloth is called tapa cloth, which was a major source of clothing for native Polynesians. The bark was obtained from the paper mulberry (Broussonetia papyrifera), a member of the mulberry family (Moraceae). Native figs, such as the Polynesian banyan (Ficus prolixa) were also used locally on some islands for bark cloth. Strips of bark were peeled off the trunk, and the outer coating scraped off with a shell. After they were soaked in water and cleaned, the strips were placed on a hard wood surface and pounded with a mallet. Individual strips were fused together by overlapping the edges and beating them together. Depending on the thickness of the sheets, the finished tapa cloth varied in appearance from a muslin-like material to a tough, leather-like cloth.

Modern paper is made from wood pulp, a mass of intermeshed fiber cells that are pressed into a thin sheet. This process was first produced by the Chinese nearly 2,000 years ago using the stem fibers of paper mulberry (Broussonetia papyrifera). The fibers were separated from the stems and floated in water. The macerated meshwork of fibers was allowed to settle in a thin film on a screen. After drying, the thin sheet of interlocked fiber cells (paper) was peeled from the screen. If you closely examine coarse blotter paper under a microscope with substage illumination, the meshwork of slender fiber cells can easily be seen, especially near the torn edges of the paper.

In order to produce pulp, logs and wood chips must be reduced to a mass of fibers. If gymnosperm wood is used, then the pulpy mass is composed essentially of tracheids. Several methods are used to convert wood into pulp, including the ground wood process, sulfite process and the sulfate process. In the sulfite process the chips are cooked in a digester with bisulfites. Hot acid is then pumped into the digester, and the cooking is completed. The softened fibers are then forcibly blown into a chamber to separate them. Paper made from this process has a high acid content and becomes brittle and begins to disintegrate after 100 years. This is why modern textbooks (including the recommended text for this course) often say "printed on acid-free paper." The sulfate process is an alkaline rather than an acid process and uses as digestive agents sodium sulfate, sodium sulfide, and caustic soda (sodium hydroxide). This process is now the most widely used because unlike the sulfite process, the "acid free" paper has greater longevity. The sulfate process also dissolves the resins out of the pulp and can therefore be used for gymnosperm woods such as Douglas fir (Pseudotsuga menziesii) and various pines, including (Pinus ponderosa). After digestion, the tenuously bound fibers are beaten to separate them.

In addition to chemically digesting the wood until it is reduced to its component fibers, the lignin must also be removed in fine quality papers. Cardboard containers and supermarket shopping bags (kraft paper) are stiff and brown because they still contain lignin. Wood pulp is also used for the manufacture of insulating board and fiberboard, such as masonite. Special types of paper, such as photographic paper, are coated so they will be suitable for various printing techniques. Rag paper contains fibers from cotton and linen. It does not become brittle and can withstand repeated folding and creasing. U.S. money is printed on rag paper with scattered colored fibers of silk or nylon to discourage counterfeiting.

Sizing agents are used to make the high quality paper of books, magazines and paper money. Sizing involves the addition of natural thickening agents such as starches, gums and resins to paper and cloth fabrics to stiffen them and to fill surface irregularities. In the paper industry sizing prevents the paper from becoming too absorbent so that writing inks will not bleed or diffuse into the paper. Some of the commonly used sizing agents mixed with paper pulp are potato starch, guar gum, methyl cellulose, alginates and rosin. Different sizing agents are used for specific attributes in the finished paper product. For example, methyl cellulose has excellent oil and grease resistant properties and also helps to give an even finish. Guar gum from the sap of Acacia senegal serves to bond the fibers together and distribute them more evenly. This gives a better sheet formation and improves folding and tensile strength.

Why Paper Money Doesn't Disintegrate In A Washing Machine? Ordinary notebook paper is made from the intermeshed cellulose fibers of wood pulp. The cellulose fibers absorb water and come apart (dissolve) when they are soaked in water. Paper money is made from textile (rag) fibers, such as cotton and linen. Intermeshed "rag" fibers bond together more firmly and don't separate (dissolve) in water. The upper right corner (red arrow) of this U.S one dollar bill is torn off. The magnified view (right) of the torn edge shows a fringe of intermeshed textile (rag) fibers. These fibers are much more durable than the cellulose fibers from wood pulp.

The stringy, threadlike strands in the leaves of monocots such as giant yucca (Yucca elephantipes), sisal (Agave sisalana), bowstring hemp (Sansevieria trifasciata) and New Zealand flax (Phormium tenax) are composed of clusters of fiber cells associated with the numerous vascular bundles.

Fibers are also present in the stems of many herbaceous dicots, such as flax (Linum usitatissimum), ramie (Boehmeria nivea) and Indian hemp (Cannabis sativa). The following table shows some of the world's most interesting and economically important fiber plants used for cordage and textiles.

Cotton "fibers" are made from unicellular hairs that grow out from the surface of the seed immediately after fertilization. The hairs are twisted into usable thread which is tough and strong. Cotton hairs (lint) of tetraploid (4n) species may be up to 50 mm long. In the cotton gin, fine brushes pull the lint off the seed by drawing it through holes too fine for the seeds to pass. Cotton thread is spun from countless billions of microscopic hairs covering the surface of cotton seeds, each hair up to 50 mm (2 inches) in length. The total length of hairs in a single cotton boll (one seed capsule) may exceed 300 miles. Imagine how many miles of cotton hairs are in a standard 500 pound bale. Cotton is the textile produced in the largest volume worldwide.

Kapok hairs are produced on the inner surface of the seed capsule of the kapok tree (Ceiba pentandra). In tropical regions of the New World (including Central and South America), the kapok grows into an enormous rain forest tree with a massive buttressed trunk. The floss silk tree (Chorisia speciosa), another member of the kapok family (Bombacaceae) also produces seed capsules lined with masses of silky hairs. This tree with its distinctive thorny trunk and showy pink flowers is commonly planted in southern California. Kapok hairs are coated with a highly water-resistant, waxy cutin. The empty lumen is larger than cotton hairs and hence the fiber is lighter in weight. Kapok is difficult to spin and is not made into textiles. It is used primarily as a waterproof filler for mattresses, pillows, upholstery, softballs, and especially for life preservers. A kapok-filled life jacket can support 30 times its own weight in sea water. The seeds of North American milkweeds (Asclepias) have a tuft of long, silky hairs at one end. Like miniature parachutes, the hairs aid in the wind dispersal of this interesting North American species. The hairs were used as a substitute for kapok during World War II. The hairs can also be twisted into dental floss. Coir fiber is made from the husk (mesocarp) of the coconut fruit (a dry drupe). In the Orient, it is twisted into rope and twine, and in the West it is made into door mats and stuffing. The dried, seed capsules of North American devil's claw (Proboscidea parviflora) are used by Native American tribes of Arizona and Mexico to weave black designs into their baskets.

Bast fibers are groups of long, thick-walled fiber cells usually occurring in the phloem parenchyma of stems. Bast fibers (and sometimes the associated xylem tissue) constitute the main source of stem fibers. Flax and ramie are fine and white, and are mainly cellulose. Jute and hemp are coarse and brownish, and contain ten to fifteen percent lignin. Flax fibers are made into linen textiles which are soft, lustrous and very water-absorbent. Linen is used for towels and numerous other products. Flax seeds are the source of linseed oil. Ramie fibers are stronger than cotton and flax, and are made into the lustrous "China grass cloth." Jute is woven into burlap, sackcloth and tough twines.

Indian hemp (Cannabis sativa) fibers are made into cord and rope, and into some textiles. The male plant yields the best fibers. The best varieties (for fiber) are grown in Italy and are almost white in color and nearly as soft as linen. Female plants are an important source of another economically important plant product (THC) which accounts for the main cash crop in some counties of California. Another Indian hemp (Apocynum cannabinum) was an important traditional fiber plant of native North American people.

Leaf fibers are derived from long, narrow leaves typical of the monocots. Sisal and henequen come from large, polyploid species of Agave. Agave sisalana is propagated vegetatively from viviparous plantlets that develop high on the inflorescence (flower stalk). Sisal and henequen furnish most of the world's non-naval string and rope. Another leaf fiber plant in the same family as Agave is the genus Yucca. The sun-dried leaves of Yucca elata are used extensively for the main visible white coils in baskets of native North American people, including the Papago, Pima and Havasupai.

Manila hemp or abaca comes from the leaves of a banana species (Musa textilis) which is native to the Philippines. Manila hemp makes the finest ropes which have held ships to docks throughout the world. Manila hemp rope is being replaced by nylon in many parts of the world. In Ethiopia, another banana species (Musa ensete) is similarly used for its strong leaf fibers. Bowstring hemp comes from the leaves of Sansevieria metalaea (syn. S. guineensis & S. hyacinthoides), and other species. The whitish fiber is used in Central Africa for course cloth and fishing nets. Some species of Sansevieria are cultivated for their rosettes of attractive, variegated leaves. Another monocot used in southern California landscaping (such as the campus of Palomar College) with tough, fibrous leaves is New Zealand flax (Phormium tenax).

Many commercially important textile fibers are made from natural wood cellulose or from synthetic polymers, and two important protein fibers come from a mammal and an insect. Some of the popular synthetic fibers include various polyesters and nylon, and some of these require natural plant products in their manufacture. Castor oil is the primary raw material for the production of sebacic acid, which is the basic ingredient in the production of nylon and other synthetic resins and fibers. Approximately three tons of castor oil are necessary to produce one ton of nylon. Purified wood cellulose (from plant cell walls) is used in the manufacture of a number of synthetic products. Cellophane is made from a viscous solution of wood cellulose that is extruded through a narrow, slit-like opening. In rayon, the viscous solution of wood cellulose is extruded through minute openings called spinnerets to form strong, pliable fibers. Arnel is made from triacetate fibers from purified wood cellulose which has been chemically bonded to acetyl groups. Wool comes from the hair of sheep and silk thread is spun from the cocoon of the silkworm moth.

The silk industry depends on moth that feeds on the leaves of mulberry trees. Raw silk actually consists of two proteins, fibroin and sericin. The fibers are very fine and lustrous, about 1/2500th of an inch in diameter. About 2,000 to 3,000 cocoons are required to make a pound of silk. Based on 2/3 of mile (1 km) per cocoon, ten unraveled cocoons could theoretically extend vertically to the height of Mount Everest, the world's highest mountain. It is estimated that at least 70 million pounds of raw silk are produced each year, requiring nearly 10 billion pounds of mulberry leaves. According to E. L. Palmer (Fieldbook Of Natural History, 1949), one pound of silk represents about 1,000 miles of filament. The annual world production represents 70 billion miles of silk filament, a distance well over 300 round trips to the sun!

Although silk thread is synthesized from digested mulberry leaves, it is technically an animal fiber rather than a plant fiber. Another fascinating animal fiber is derived from the webs of spiders. In fact, the world's strongest natural filament comes from the silk strands of a spider's web, specifically orb weaver spiders of the genus Nephila (family Araneidae). The golden silk spider (Nephila clavipes) of the southeastern United States and New World tropics makes a huge web more than three feet (1 m) in diameter.

The golden orb's web can run from the top of a tree 20 feet (6 m) high and up to six feet (2 m) wide. Unlike the fragile webs of other spiders, the golden orb's web can last for weeks and even months. The silk of Nephila species is so strong that it can trap small birds, which the spider doesn't eat. Trapped birds often destroy the web by thrashing around. To avoid such damage, the spider often leaves a line of insect carcasses on its web (like the safety strip on glass doors), or builds smaller barrier webs around the main web. Matted and twisted webs of Nephila maculata are used by South Sea Islanders for various kinds of bags, fishing lures and traps. Female spiders are induced to build nests on bamboo frames which are then used as fishing nets. In the Solomon Islands, the spider web is collected by winding it around sticks to make large sticky balls which are suspended just above the water. Needle fish are lured to jump out and get entangled in the ball. In Southeast Asia, people make a net by scooping up the web between a stick bent into a loop. Spider webs have also been used as a bandage to stop blood flow from an injury.

The silk of golden orb spiders is almost as strong as Kevlar, a synthetic fiber which is drawn from concentrated sulphuric acid. [According to Stanton de Riel (Personal Communication 2013), literature suggests that ultra-high molecular weight polyethylene (UHMWPE) yield strength: weight ratio (the usual criterion of strength) exceeds that of polyaramid (Kevlar) by 40%.] If spider silk could be manufactured, it would have thousands of uses, including parachutes, bullet-proof vests, lightweight clothing, seatbelts, and light but strong ropes. It could also be used for sutures in operations, artificial tendons and ligaments. It has been estimated that a solid strand of silk from this spider the diameter of a pencil could stop an airliner in flight! This unsubstantiated claim was reported on a TV nature program.

Studies are now being conducted to have genetically engineered plants produce fluid polymers that can be processed into silk. Spiders are not used commercially to produce silk fabric because silkworm moth caterpillars produce twice as much silk and are much easier to culture. Up to 150 meters of silk can be collected from a single individual of Nephila clavipes. It would take approximately 415 spiders to make a square yard of cloth. The same number of silkworm larvae could make twice as much silk, and they don't eat each other. All you need is a plentiful supply of mulberry leaves.

Return To WAYNE'S WORD Home Page Return To NOTEWORTHY PLANTS Page Go To Biology GEE WHIZ TRIVIA Page Go To The LEMNACEAE ON-LINE Page

All text material & images on these pages copyright © W.P. Armstrong