Читать книгу Encyclopedia of Essential Oils: The complete guide to the use of aromatic oils in aromatherapy, herbalism, health and well-being. - Julia Lawless - Страница 26

Over thirty families of plants, with some ninety species, represent the main oil-producing group. The majority of spices (allspice, cardamon, clove, nutmeg, ginger, etc.) originate in tropical countries; conversely, the majority of herbs grow in temperate climates (bay, cumin, dill, marjoram, fennel, lavender, rosemary, thyme, etc.). The same plant grown in a different region and under different conditions can produce essential oils of widely diverse characteristics, which are known as ‘chemotypes’. Common thyme (Thymus vulgaris), for example, produces several chemotypes depending on the conditions of its growth and dominant constituent, notably the citral or linalol types, the thuyanol type, and the thymol or carvacrol type. It is therefore important not only to know the botanical name of the plant from which an oil has been produced, but also its place of origin and main constituents. One of the main ways of defining the qualities of a particular oil and checking its purity is to ascertain the specific blend of/components and look at its chemical character.