120 ELEMENTARY BOTANY. 



In North America it is obtained from the Balsam Fir {Abies hat- 

 samed), White Pine (JPinus strobus), Red Pine {Pinus resinosa), 

 Loblolly or Old Field Pine (Pinus tseda), and Broom Pine 

 {Pinus palustris). Turpentine is found both in the cortex and 

 wood. The better kinds are thin and clear ; those of poorer 

 quality are thick and cloudy. They find extensive use in the 

 manufacture of varnish, sealing-wax, soaps, etc. The finer 

 kinds are used in medicine. That called Venetian turpentine 

 is obtained from the European Larch. The finest of all tur- 

 pentines is the Canada Balsam, from the Balsam Fir. Com- 

 mon resin (or rosin) is the mass remaining after the natural 

 escape or removal by distillation, of the volatile oil from the 

 turpentine. Wood after yielding resin is often used in the 

 manufacture of tar, illuminating gas, creosote, paraffine and 

 aniline. Other important resins are Balm of Gilead, Mastic, 

 Sandarac, Damar, Gum Lac, Copal, etc. 



3. Gums occur very commonly. They are homogeneous 

 exudations from many trees, arising by a metamorphosis of 

 tissue, or rarely by a chemical change of the starch. They 

 are soluble (or soften) in water and are insoluble in alcohol. 

 The color may be yellowish, brownish, reddish, seldom white 

 or black. The powder is always white. Gums are carbo-hy- 

 drates, containing carbon, hydrogen and oxygen, but no nitro- 

 gen. They are of little or no dietetic value. For mucilage 

 their use is very general, but the largest quantity is consumed 

 in stiffening fabrics and producing a glazed surface upon them. 

 Gums are often added to fluids to increase their density, so 

 they will hold in suspension pigments or other added sub- 

 stances. The most important gum is that obtained from the 

 species of Acacia (Bean family). The plants are generally small, 

 spiny trees or shrubs, growing in Africa, Arabia and other 

 countries, often forming vast forests. The gums from the dif- 

 ferent countries usually have different names, as Gum Arabic, 

 Cape Gum, Gum Senegal, Australian Gum, etc. From plants 

 belonging to the genus Astragalus (Bean family) of Greece, Asia 

 Minor and Persia, Gum Tragacanth is obtained. It is softer than 

 Gum Arabic, swells up in water, but is only partially soluble. 



