CHAPTER XIII. 

 ECONOMIC BOTANY. 



«>XKo« 



1. The useful products furnished by the vegetable kingdom 

 are extremely numerous. Only the more prominent can be 

 brieflj' mentioned. Perhaps none occur more widely than the 

 Resins. They are found in nearly all groups of plants, even 

 in the mycelium of Fungi. Their occurrence is mostly in the 

 cortical portions of plants, yet they have been found in all 

 tissues except the cambium. The resins are hydrocarbons, 

 being rich in carbon, containing but little oxygen and no nitro- 

 gen. They contain resinous acids, volatile oils, gums, carbon- 

 aceous substances, cellulose, tannin, etc. The color is usually 

 between yellow and brown, but may be red, white or black. 

 Resins arise by a metamorphosis of tissue, etc., or they are 

 a product of secreting cells. Gamboge used extensively for 

 coloring varnishes, etc., is a resin furnished bj'^ Gardnia morella, 

 a small tree belonging to the Gamboge family (GuWferas). It 

 occurs in Ceylon, Siam, Cambodia (or Cambogia, whence the 

 name). The resin is obtained by making incisions in the 

 stem, out of which it flows. Asafcetida is an exudation from 

 the stems of two plants of the Parsley family ( Umbelliferse). 

 These grow in Southwestern Asia. 



Specimens of most of the vegetable products mentioned in this chapter 

 can be obtained. They should not be used merely as illustrations (though 

 highly desirable for such purpose), but careful examination of them accom- 

 panied by notes and drawings should be a part of the regular class-work. 



2. The Turpentines of commerce come mainly from Europe 

 and North America. In the former country the Firs (Abies) 

 and Larch {Larix europasa) yield this oleo-resinous substance. 



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