As there are a great many aromatic vegetable substances, so there are numerous odors, or, to retain the customary though incorrect appellation, numerous essential oils. All of these, however, cannot be used in the art of perfumery, as some of them do not possess a pleasant odor, as is the case, for instance, with oil of turpentine. (We may state here, however, that very pure oil of turpentine, distilled from certain Coniferæ, has an agreeable, refreshing odor which at present has found application in perfumery under the title of forest perfume or pine-needle essence.) Besides, there are numerous essential oils which, while possessing a very pleasant odor, still cannot be used in perfumery except for very cheap preparations, though they are employed in much larger quantities in the manufacture of liqueurs. Such oils are: oil of cumin, fennel, juniper, absinth, etc. As we shall return to this subject in connection with the essential oils which are used in perfumery in general, we will now consider at greater length the aromatic vegetable substances which are employed for the manufacture of fragrant odors. CHAPTER IV. THE AROMATIC VEGETABLE SUBSTANCES EMPLOYED IN PERFUMERY. Every fragrant portion of a plant can be used for the preparation of an aromatic substance, and therefore for the manufacture of a perfume. Hence we are unable, in the following enumeration of the aromatic vegetable substances, to make any claim to absolute completeness; for every new scientific expedition may acquaint us with hitherto unknown plants from which the finest odors may be obtained. We have said above that we have not yet even fixed in our perfumes all the odors of the known aromatic plants, and therefore there is still a large field open to the progressive manufacturer. In the following pages we must restrict ourselves to the description of those aromatic vegetable substances which are used in the laboratories of the most advanced and scientific perfumers for the manufacture of odors. At the same time we lay particular stress on the fact that the knowledge of these raw materials is a matter of the greatest importance to the manufacturer of perfumes because it enables him to appreciate the differences, often very minute, between fine and inferior qualities. Every manufacturer who aims at the production of fine goods must make it the rule to use nothing but the best raw materials.