224 INDUSTRIAL PLANTS 
transported, require light fibrous material so soft and elastic that 
it will fully occupy the spaces into which it may be crowded. Paper 
consists of fibers, especially rich in cellulose, which have been soft- 
ened and compacted, and finally pressed into sheets or molded into 
other forms as papier-maché. Besides the more familiar uses of 
paper for writing, drawing, printing, book-binding, boxes, and so 
on, there are many others of considerable importance. Thus we 
have paper garments, paper napkins and other substitutes for fab- 
rics used in the household, paper pails and similar articles replacing 
-wooden ware, paper canoes and paper car-wheels. Such wheels hav- 
ing steel hubs and tires, are found to wear far better than wheels made 
wholly of steel. Fine paper is nearly pure cellulose. The larger the 
percentage of cellulose in a fiber the better the paper it makes. 
Fibers rich in cellulose are also the source of various cellulose prod- 
ucts, obtained by chemical means presently to be described. These 
products include guncotton which is a high explosive used in the 
manufacture of smokeless powder; collodion, of much use in surgery 
as a covering for wounds; celluloid, the well-known substitute for 
ivory, bone, tortoise-shell, and similar materials; and artificial silk 
which is coming to be used widely in place of the product of the silk- 
worm. 
From what has been said of the great variety of uses to 
which fibers are put, it follows that the term fiber must have 
a rather broad definition. Fibers may be either fine or coarse, 
flexible or stiff, elastic or soft. They differ also in structure 
and chemical composition, and in the part from which they 
are derived. They agree, however, in being comparatively 
slender structures, which although separately weak, form 
strong yet pliable articles of manufacture when twisted, 
woven, or otherwise intimately joined together. If we define 
fiber-plants as those which yield slender parts of economic 
use when thus united, it may be said that over a thousand 
species of them are known to be used more or less in various 
parts of the world. The great majority of these, however, 
are used only in restricted regions and are not cultivated. 
Less than fifty are of much commercial importance. Of 
these the most useful are the species yielding cotton, flax, 
jute, hemp, and manila. 
Fibers may be classified most conveniently for our present 
purpose into the following groups: (1) surface fibers, more or 
less hair-like outgrowths; (2) bast fibers, consisting entirely 
of such tough strands as form the bast or strength-giving 
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