-Advertisement-
  About AE   About NHM   Contact Us   Terms of Use   Copyright Info   Privacy Policy   Advertising Policies   Site Map
   
Custom Search of AE Site
spacer spacer

Microbes & History:
Microbial influence on the spread of Civilization

Mark Stephansky



This activity was originally developed under a grant from the Council for Basic Education; The Sci-Mat Fellowship program.

Type of Entry:

  • Lesson/Class Activity

Type of Activity:

  • Hands-on activity
  • Simulation
  • Group/Cooperative Learning

Target Audience:

  • Biology (Most applicable)
  • Life Science
  • Advanced/AP Biology
  • Integrated Science (1,2,3 or 4)
  • Special Education (visually impaired)


Background Information:

What question does this activity help students to answer?

The following activity will show the student how to extract plant fibers from the flax plant Linum usitatissimum in the process of making linen fibers. Doing so will serve to spark interest in the importance of microbial action on the spread of human culture and civilization throughout the world.

Notes for teacher: A detailed study of the flax plant, Linum usitatissimum, is an excellent activity to integrate biological science with the humanities. Living up to its name, usitatissimum means ´most useful', the flax plant, used as a source of fiber for the making of blankets, handkerchiefs, paper, clothing and sails, became a valuable commodity, indeed a staple of life during the 17th and 18th centuries. Its importance to world societies can be traced all the way back to ancient Egypt, Phoenicia, Mesopotamia, Greece, and Rome and through its use as a sail cloth, is also perhaps the main contributor to the spread of human culture throughout the world.

The use of flax/linen as an acceptable sail material was especially important to the world's greatest explorers. The renowned Mayflower, along with many other ships associated with our early history, had sails made from the plant's fibers. Flax was of such commercial importance in colonial America that a school for its making was established in Boston. Later, during the Revolution when England's General Howe reported that "linen goods were much wanted by the rebels" he gave the order to carry away all of Boston's linen when British forces evacuated the city. In many respects preindustrial societies did indeed center on the use of flax. This valuable commodity was and still is dependent upon two soil microbes, Clostridium felsineum and Clostridium pectinovorum.

Flax is an annual plant and, under favorable conditions grows to a height from two to three feet. The plant is characterized by bright blue flowers and a field of flax in full bloom is said to have the appearance of an inland sea. Ripened, the plants are carefully uprooted in order to preserve their fiber length and laid out to dry. Once dried, they are sorted according to size, loosely bundled and placed onto moist fields or submerged into slowly flowing streams or stagnant pools. The Clostridium bacteria, ubiquitous in soil, then begins to grow on the flax and digest pectin, a major substance of the plant. This process of "retting" the flax loosens the flax fibers preparatory to spinning.

Required of students:

No special requirements are necessary.

Preparation time needed:

This activity requires significant preparation in one important aspect; the growth and subsequent harvest of the flax plants during the summer prior to their use in the classroom. Alternatively, the plants may be sown in a classroom or greenhouse where their entire life cycle can be utilized in a plant study unit.

Class time needed:

The entire experiment will take approximately 3 weeks to complete. The actual in-class, hands-on time will require 1-2 initial days of preparation work, 10-12* days of bacterial action (during which the students make daily brief 5 minute observations), and finally 1-2 days for completion and wrap-up.

*Time may be significantly shortened.


Abstract of Activity

An excellent activity to integrate biological science with the humanities is a detailed study of the flax plant Linum usitatissimum. Living up to its name. (usitatissimum means ´most useful'), flax has been utilized for centuries not only in ancient Egypt and many other early civilizations for making linen cloth, but is also perhaps the main contributor to the spread of human culture throughout the world.

Native to Eurasia, flax was the major source of cloth fiber (real linenânot the polyester variety) until the growth of the cotton industry. A versatile plant, not only were its fibers used to make cloth, but its seeds were crushed to make linseed oil. The remaining linseed cake was used for fodder.

The main focus of this exercise is on the historically important part of the flax plant, the fibers, which are located in the stem between the woody xylem and the thin outer bark. These fibers run the length of the stem from the root to the flowers and provide support for the growing plant. Holding the plant together is a sort of natural glue or pectin. One type of pectin holds the fiber cells into bundles and another attaches the bundles to the bark and the core of the stem. During this exercise students observe how a ubiquitous soil bacterium Clostridium pectinovorum breaks down this glue thereby releasing the fibers. From the hands-on activity a discussion emerges centering on the role that microbial action plays on the spread of human civilization.


Lesson/Activity

Materials Needed:

1. Harvested, dried flax plants. Flax Seeds Linum usitatissimum are available from the Heirloom Seed Project, The Landis Valley Museum, 2451 Kissel Hill Rd. Lancaster, PA 17601 $6.20/lb +S/H

2. A small shrub rake or child's yard rake (for the rippling process; to remove the seed pods)

3. A large deep tray (to submerge flax stalks for retting). Suggestions: On a large scale; a small child's wading pool or an old bath tub. On a small scale, (meaning the flax stalks would probably have to be cut), a rubbermaid or similar brand plastic storage bin or aquariumäavailable locally.

4. Rolling pin or heavy wooden mallet. (used in the breaking process, to separate the linen fibers from the woody core of the plant)äavailable locally.


Procedure

The first thing you must do to the dried straw is remove the seed pods in a process called "rippling". This requires a flax ripple, a tool with long steel or wooden tines resembling a rake. A bundle of the straw is pulled through the ripple starting at the root end. The seed bolls are easily removed and should be caught in a sheet, crushed and the seeds retained for use with next seasons crop.

The next step in the preparation of the flax straw is not only the most exciting, biologically speaking, but also the most challenging. This process is the retting of the flax, and to accomplish it requires the assistance of some of the most ubiquitous organisms on the earth. Retting is the delicate process in which soil microbes, either Clostridium pectinovorum, Clostridium felsineum, or a fungus depending upon which retting process is utilized, dissolve the pectins which hold the linen fibers to the stem of the flax plant. The two traditional retting processes are land (dew) retting (not recommended due to the time involved and will therefore not be discussed) and water retting. (Fungi are responsible for land retting while bacterial action takes care of water retting.) The following step-by-step approach should guide you through the process.

Water Retting

Water retting can be done in a pond, at the edge of slowly moving water, or in a tank. The latter method would seem the most convenient for a classroom activity. In addition it is a much quicker process being completed in 10-12 days in water kept at 62┴F to 68┴F. The retting will proceed even faster, 3-4 days in water kept at 95┴F.

Some important reminders:

  • Some water must be exchanged, i.e., there must be some water movement. A third of the water should be removed each day and be replaced with fresh water at the same temperature.
  • A system of weights must be improvised to keep the bundled fibers submerged as gases from the fermentation process will collect and buoy the straw bundles.
  • A vented area is necessary as a sour yeasty smell begins to arise due to fermentation.
  • When the retting is complete (see below for test), the fibers should be rinsed with fresh water to halt the bacterial action.
  • To determine if enough time has transpired, simply dry the flax and proceed to the next step (breaking). If the fibers still cling to the core, further retting is required. Resubmerge the flax and check after a few hours.
  • After retting, the straw must be thoroughly dried again before the next process begins.

Breaking:

This process usually requires a flax brake, a wooden device consisting of two hinged blades. Actually the bottom hinge has three blades while the top only two. The blades fit together and when used in a chopping motion, closing the top hinge against the bottom, a handful of straw is separated into bits and pieces of pith and bark (called shives or boon) and the long lustrous linen fibers. The bits that remain after breaking will be removed by scutching. In this activity flax breaking is done with the aid of a rolling pin or mallet.

This is a very dusty job and is best done in a well ventilated area or if possible out▄doors. For classroom demonstrative purposes, simply supply each student with a few stalks and have them snap the woody core (as they might a pencil) to release the linen fibers.

Extension/Reinforcement/Additional Ideas:

As stated in the notes to the teacher this activity is very conducive to cross curriculum work especially within the humanities. To that end additional information is included below.

In the production of linen fibers for the making of cloth, additional steps (scutching and hackling) would follow the breaking procedure described above.

Scutching

Scutching the flax is done to remove the bits of woody stem that remain after breaking. During the scutching process, a handful of straw is drawn across a wooden scutching block and struck with a wooden scutching knife in such a way that it removes the clinging bits of boon. The bundle of fiber is continually turned during the procedure and when finished should be completely free from all woody pieces. If there is very difficult to remove the woody bits, it is an indication that the retting process was incomplete and the bundle should be returned to the retting tank. If, on the other hand the fibers simply fall apart in your hands, it has been over▄retted.

Hackling

The final stage before the linen fibers are to be spun is the hackling process. Hackling is the process of combing the linen fibers through various grades (from coarse to medium to fine) of hackles to clean and separate the long line fibers from the short tow fibers. A hackle is composed of a wooden base into which are set rows of steel pins or teeth. (Hackles are graded, based upon the number, size, and spacing of the teeth.) Hackling is a slow gradual process. Handfuls of flax fibers, held by the root ends, are lightly drawn across the hackling teeth beginning with the tips of the fibers. Gradually the process continues until one reaches the middle of the fiber bundle. At this point you flip the bundle and grasp it by the tip ends and comb from the root ends to the middle. If you wish to use the bundles of hackled line flax for weaving, some care must be made to keep the fibers in order or else a jumbled mess would result. Stored flax will last indefinitely.

Historical Importance

Though not known for certain, there is strong reason to believe the origin of flax can be traced to the Caucasus, between the Persian Gulf, the Caspian Sea, and the Black Sea. Flax fibers are among the oldest and strongest known to man. In fact the oldest woven cloth on record is that of linen. The use of natural fibers for clothing has been described as the greatest discovery, second to fire that is, made by primitive man. Evidence for the use of natural flax fibers has been found in Stone Age Swiss Lake dwellings. In fact nearly every civilized culture has been associated with its use. The importance of flax can be summed up in one statement written by Pliny the Elder (c52 A.D.) in his Naturalis Historia.

"How audacious is life and how full of wickedness, for a plant to be grown for the purpose of catching the winds and the stormsâout of so small a seed springs a means of carrying the whole world to and froâ."

The application Pliny was referring to was the use of flax fibers in the making of linen sails of sea-faring ships. As mentioned above, even the scientific name of the plant Linum usitatissimum, suggests it universal appeal, the second name means most useful or most used.

Ancient Egyptians knew the flax plant well, as did the Phoenicians, Assyrians, Babylonians and Hebrews. The spread of the use of flax has been traced from Egypt to Greece, Rome, France, Spain, Holland, Flanders and the British Isles.


References:

Chase, M. (1992). Flax from Seed to Fiber. Spin Off: The Magazine for Handspinners, 16, 62-69.

Chase, M. (1982). Flax Processing. The Weaver's Journal, 7, 5-9.

Heinrich, L. (1992). The Magic of Linen: Flax Seed to Woven Cloth. Victoria, B.C.: Orca Book Publishers Ltd.

Margulis, L. and Sagan, D. (1988). Garden of Microbial Delights. Boston: Harcourt Brace Jovanovich


Fellows Collection Index


1996 AE Collection Index


Activities Exchange Index


 
Custom Search on the AE Site

 

-Advertisement-