Economic Importance of Plants 263 



by oxidation. Gutta-percha is used in making surgical instruments, orna- 

 ments, golf balls, coverings of cables, tubes, etc. 



Resins are like the elastic gums in that they are secured from certain 

 plants by tapping them for their juices. Resins are mixtures of several 

 different oxidized hydrocarbons (hydrogen and carbon). They are 

 inflammable, insoluble in water, usually liquids which harden when 

 oxidized. The common resin is obtained from the pitch or resinous sap 

 of pine trees. Sometimes a gum and resin are united as a gum resin, 

 such as asafetida. Resinous materials of various types are common in 

 many plants. Two common examples are rosin and copal. Rosin is the 

 most widely used of resinous materials. It is one of the products which 

 remain when turpentine is distilled. Turpentine flows from the pine 

 and other cone-bearing trees. Rosin is used in the manufacture of var- 

 nish, yellow soap, certain cements, sealing wax, cheap candles, certain 

 medicinal ointments, etc. Copal is the name applied to a large variety of 

 resins which occur naturally in hard, amberlike masses. Corpal is used 

 in the manufacture of certain types of varnish. Amber is a yellowish, 

 translucent, fossilized resin resembling copal. It is used in the manufac- 

 ture of pipe stems, amber beads, and certain types of varnish. When 

 polished by friction, it becomes highly electric. 



Coloring Matters (Dyes). — Coloring matters of various kinds are 

 quite common in the plant kingdom but often of questionable or un- 

 known benefit to the plant which produces them, in which case they are 

 probably waste products of their metabolic activity. 



Indigo blue (CieHioNsOo) was first used in India many hundreds of 

 years ago and is derived from indican (C26H31NO17), an aqueous extract 

 from the leaves of the indigo plant (pulse family) . 



Haematin (CieHisOe) is a violet -purple dye derived from the color- 

 less material haematoxylin (C16H14O6) obtained from the logwood tree 

 (pulse family) . 



Gamboge is a resinous, gummy material secured from the bark of 

 various species of gamboge trees (gamboge family). When solidified, 

 the bright, transparent, yellowish material is used as a coloring material 

 in lacquers, varnishes, and certain paints. 



Tanbark is obtained from the bark of such trees as chestnut, oak, 

 willow, spruce, hemlock, and larch. The bark is rich in tannin 

 (C14H10O9 + 2HoO), which is used in medicine, in dyeing, and in the 

 manufacture of ink and leather. In the preparation of skins by the 



