3" 



CHAPTER XI. 



PLANTS PRODUCING GUMS AND RESINS. 



GUMS. 



Dr. Hubert Jacob de Cordemoy, in his valuable work, 

 " Gommes, Resines d'origine exotique," divides gums into 

 three categories : — 



(i) True gums. 



(2) Pseudo gums. 



(3) Tano gums or kinos. 



By true gums is meant those which are completely or 

 for the greater part soluble in water (gum arable). 



Pseudo gums are substances w^hich swell up in water 

 without dissolving in it (gum tragacanth). 



Kino gums are those which contain gallic acid and tan- 

 nins in addition to substances which give rise to muci- 

 laginous solutions when mixed with water. 



According to Guerin Varry, the three proximate con- 

 stituents of gums are : Arabin, completelv soluble in water ; 

 cerasin, isomer of the foregoing, which swells up in water 

 and remains insoluble; bassorin, which is likewise insoluble 

 but swells up in water and forms a gelatinous mass. 



According to Fremy, soluble gums are composed of 

 metagummic acid, which dissolves on combination with 

 traces of a base. Calcined gums leave a residue of mineral 

 matters in proportions which vary with different gums. 

 According to Groeger, gum arabic dried at 100° C. gives 

 3'56 per cent, of ash, composed of lime, potash, and 

 magnesia. 



Bassora gum (Acacia leucophloea) is formed, according 

 to Fremy, of an acid, gelatinous substance, which should 



