458 PLANTS AND THEIR RELATION TO MAN 



yield fine fibers, but if they are less crowded, they develop into 

 strong and hardy plants and yield coarse fibers. If the plants 

 are pulled when young before their seeds are ripe, the fibers are 

 fine, but if they are allowed to grow until their seeds have 

 ripened, the fibers are coarse. 



Stem fibers are not the only ones suitable for commercial 

 purposes. The leaves of the pineapple plant contain fibers of 

 unusual strength and fineness, from which fabrics of the most 

 delicate texture are woven. The fibrous husk which incloses 

 the hard-shelled coconut contains tough enduring strands 

 which make excellent doormats and mattings. 



Commercial products. For years rubber has been used for 

 carriage and wagon tires, overshoes, waterproof garments, life 

 preservers, hose, elastic bands, erasers, and other purposes. 

 But the greatest demand for rubber has arisen since the 

 large and heavy tires of automobile cars and trucks require 

 vast quantities of them. Rubber is obtained from trees which 

 grow in tropical countries (Fig. 326), the finest grades coming 

 from India, Brazil, and the Amazon Valley. Cuts are made in 

 the trunk of the tree and cups are placed to receive the milky 

 juice or latex which flows from the wounds. The juice re- 

 sembles cream in appearance and consists of minute globules of 

 rubber floating in water. The making of rubber from latex is 

 similar to the making of cheese from cow's milk. The globules 

 of rubber are separated from the watery mass, and are pressed 

 into sheets or into balls. 



Turpentine is one of the most important and widely used oils 

 obtained from plants. It is used for dissolving and thinning 

 paints and varnishes, and most of us are familiar with the 

 strong odor of it in freshly painted houses. Turpentine is fre- 

 quently substituted for quinine in fevers, and is used as a lini- 

 ment in bandages. Crude turpentine is a thick, sticky liquid 

 which flows from wounds made in the long-needle pine tree. 



