BITTER SECRETIOX. 65 



landine, Cherulonium iiiajus, Engl. BoL t. 1581, and 

 some plants allied to it, the emulsion is orange-co- 

 loured. 



The more refined and volatile secretions of a resi- 

 nous nature are called Essential Oils, and are often 

 highly aromatic and odoriferous. One of the most 

 exquisite of these is afforded by the Cinnamon bark. 

 They exist in the highest perfection in the perfumed 

 effluvia of flowers, some of which, capable of combi- 

 nation with spirituous fluids, are obtainable by distil- 

 lation, as that of the Lavender and Rose; while the 

 essential oil of the Jasmine is best procured by immers- 

 ing the flowers in expressed oil, which imbibes and 

 retains their fragrance. Such Expressed or Gross Oils, 

 as they are called, to distinguish them from essential 

 oils obtained by distillation, are chiefly found in the 

 seeds of plants. In the pulp of the Olive indeed they 

 occur in the form of an emulsion, mixed with watery 

 and bitter fluids, from which the oil easily separates by 

 its superior lightness. These expressed oils are not 

 soluble in spirits or water, though by certain interme- 

 diate substances they may be rendered capable of 

 uniting with both. 



The Bitter secretion of many plants does not seem 

 exactly to accord with any of the foregoing. Some 

 facts would seem to prove it of a resinous nature, but 

 it is often perfectly soluble in water. Remarkable in- 

 stances of this secretion are in the Cinchona qficinaUs. 



