Page:An introduction to physiological and systematical botany (1st edition).djvu/102

72 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 combination with spirituous fluids, are obtainable by distillation, as that of the Lavender and Rose; while the essential oil of the Jasmine is best procured by immersing 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 intermediate 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 instances