340 ESSENTIALS OF BOTANY 
rosin used by tinners. The liquid evaporates and is con- 
densed, while the rosin is left behind in the still. 
Tanning is mainly done by the use of infusions of vari- 
ous kinds of astringent bark. In this country the bark of 
the black oak and the Spanish oak is largely used. Hem- 
lock bark is also employed and is often. treated in the 
forests where the trees are felled, to obtain a thick ex- 
tract, which is shipped in barrels to the tanneries. Twigs 
and leaves of American and Sicilian sumach are used in 
tanning some of the thinner and finer kinds of skins, and 
imported extracts made from several tropical trees are 
employed in some tanneries. 
India rubber is made from the sap of several trees and 
lianas found in the tropical regions of both hemispheres, 
and gutta-percha is yielded by trees of the tropical Star- 
apple family, which also produces many edible fruits. 
(6) PLANT FIBERS, HAIRS, AND SIMILAR PRODUCTS 
415. Many of the most valuable plant fibers, such as 
flax and hemp, are manufactured from the hard bast, 
others, as cotton, are composed of plant-hairs. Sometimes 
the whole stem or leaf of the plant is braided into a fabric, 
as in the case of straw hats and similar articles. 
Sedges (Cyperus) are woven into East Indian and Chi- 
nese mattings. 
Grasses of several genera (including some of the grains) 
are braided into hats, mats, baskets, and other articles. 
Straw and the coarse, tough esparto grass from Spain and 
North Africa are used in paper-making. 
Palms yield abundant supplies of fiber, and that of the 
husk of the cocoanut is used to make rope, mats, and brushes. 
