THE HESINS. 247 



Rays. Its important chemical constituents are bassorin 

 (called also tragacanthine), some arabin, cellulose, starch, 

 water (11-17 per cent.), and mineral substances. Of the 

 latter about one-half consists of calcic carbonate. Its uses 

 are similar to those of Gum-Arabic. The best qualities 

 are employed in dyeing cotton, and finishing silk and lace; 

 the poorer sorts are used in finishing sole-leather. Gum 

 of Bassora, from Bassora, near the head of the Persian 

 Gulf, belongs to the same class of gums as tragacanth. 



THE RESINS. 



211. The Resins are the most widely occurring of all 

 vegetable prod uets. They are found in nearly all groups of 

 plants, even in the mycelium of some Fungi. They occur 

 mostly in the cortical part of plants, yet have been found 

 in all tissue except the cambium. They are rich in car- 

 bon, contain but little oxygen, and no nitrogen. Their 

 composition is very complex ; they contain resinous acids, 

 volatile-oil, gums, carbonaceous substances, cellulose, tan- 

 nin, etc. They seem to be products of slow oxidation. 

 As regards structure, they are mostly amorphous, though 

 many of the turpentines contain crystals of abietinic acid. 

 The color is usually between yellow and brown ; but may 

 be red, white or black. Some are transparent, others are 

 opaque. They have generally a vitreous lustre, but some 

 are lustreless. The streak they make is mostly white. 

 Dragon's-blood and some others are exceptions. Organic 

 inclusions are very often present. The resins either arise 

 by a metamorphosis of tissue, etc., or are a product of secre- 

 tion. They may be classified into three groups, namely : 

 (1) Common Resins, (2) Resinous Gums, and (3) Balsams. 



212. Gamboge found its way into Europe from the 



