The Science of Paper in a Nutshell:  Chemistry and Botany
by Catherine Nash

The Botany of Plant Fibers   (see more info:  Beater Finesse for the Artist   in the Article section on this site)
Cellulose - almost pure form in cotton, linen, etc.  Polymers for a union of  molecules in a shain, end to end.  Carbohydrate.
Lignen - these starches must be removed by cooking to create archival paper.
Hemicellulose - Substance released during beating when water penetrates fibril wall.  Glue-like properties aid in fiber bonding during sheet-forming.

Therefore paper is defined as a felt or web of fibrous cellulosic material of uniform thickness, color, strength, and surface.  Cellulose is beaten (refined and bruised) in order to hydrate (assimilate with water) to form a wet pulp of adequate cohesive quality. 

Papermaking Fibers  (see more info:  Cooking and Blenderizing Plant Fibers in the Article section on this site)
Basically plant fibers that are suitable for papermaking are bast fibers, leaves or grasses.  Bast fibers have the highest yield, while leaves and grasses have the lowest and require large quantities to create enough pulp.  However, despite the extra work, their unique qualities and palette may be worth the effort!

If you are interested in experimenting with local indigenous plants, Lilian Bell’s book Plant Fibers for Papermaking is an excellent reference.  Also there is an addendum by Winifred Lutz in the back ot Timothy Barrett’s Japanese Papermaking if you are lucky enough to find a used copy as it is currently out of print!

Bast Fibers- Kozo (mulberry bark), Gampi, Mitsumata, Flax, Hemp
Seed Hair Fibers- Cotton, Coconut Husk Fiber (coir), Kapok
Leaves/Grasses- Wheat Straw, Abaca (banana stalk/leaves), agave (sisal), iris, narcissus,  etc...

The Chemistry of Cooking  (see more info:  Cooking and Blenderizing Plant Fibers in the Article section on this site)

Time varies from 2 to 8 hours, depending on fiber.  Soak fiber overnight.    I fill a large cooking pot (stainless steel or enamel only!) with water and slowly add the measured caustic to the cold water (NEVER the other way around.  Water poured onto caustic can explode in your face!) Bring the water to a boil and add the soaked fiber.  Rubber gloves and goggles are required.  Cook outside to avoid fumes.  Lye = dangerous stuff!

Soda Ash:  With oriental bark fibers and softer self harvested garden refuse such as iris or narcissus, cook with soda ash (NaOH).  Use a ratio of 20% soda ash to the dry wieght of the fiber, (i.e. if you have 1 pound of fiber use 20% of a pound.)   
 
Regarding Lye:  Seemingly, every papermaker I’ve ever interviewed about the proportion of lye to fiber has a different answer.  Kathryn Clark of "Twinrocker Paper" suggests that each fiber is of different strength, therefore needing different percentages of lye to the dry weight of the fiber are necessary. (this method would uphold the highest integrity of each different fiber, but requires a lot of experimentation.)  Marilyn Wold, originally of "Wild Fibers" in Hawaii, now living in Aloha, Oregon, advises adding 1 Tablespoon of Lye to each 2 quarts of H2O.
Generally, I use 9% lye to dry wieght of the fiber, as suggested by Twinrocker Paper, and throw in an extra teaspoon for good luck. (This is why I’m a paper artist and not a papermaker!)   Caution:  always add lye to cold water and not water to lye!! 

Consider using pH test strips to accurately bring the cooking water to a pH of 11 or 12 when adding soda ash or lye, rinsing afterwards to return to a neutral pH of 7.

Rinsing:  Wear Rubber Gloves!   All fiber must be thoroughly and repeatedly rinsed to remove lye or soda ash.  Paint straining net bags are available at paint stores and are made to fit 5 gal. buckets.  They work wonderfully!  The dark liquid after cooking, called liquor, left over from cooking, should be neutralized to a pH of 7.  Use either citric acid (used for canning) or vinegar.