ODORS AND LIFE. 191 



by the name of essences or essential oils. In most cases 

 the essence is concentrated in the flower, as occurs with the 

 rose and the violet. In other plants, as in bent-grass and 

 Florence iris, only the root is fragrant. In cedar and san- 

 dal-wood, it is the wood that is so ; in mint and patchouli, 

 the leaves ; in the Tonquin bean, the seed ; in cinnamon, 

 the bark, which is the seat of the odorous principle. Some 

 plants have several quite distinct fragrances. Thus the 

 orange has three : that of the leaves and fruit, which gives 

 the essence known by the name of " petit-grain ; " that of 

 the flowers, which furnishes neroli ; and, again, the rind of 

 the fruit, from which essence of Portugal is extracted. A 

 great number of vegetable odors belong exclusively to 

 tropical plants, but the flora of Europe furnishes a large 

 proportion of them, and almost all the essences used in per- 

 fumery are of European origin. England cultivates laven- 

 der and peppermint largely. At Nimes, gardeners are par- 

 ticularly attentive to rosemary, thyme, petit-grain, and lav- 

 ender. Nice has the violet for its specialty. Cannes ex- 

 tracts all the essences of the rose, the tuberose, cassia (the 

 yellow acacia), jasmine, and neroli. Sicily produces lemon 

 and orange ; Italy, bergamot and the iris. 



What, now, is the chemical nature of the odorous prin- 

 ciples in plants ? The chemistry of to-day reduces almost 

 all of them to three categories of well-ascertained sub- 

 stances : hydrocarburets, aldehydes, and ethers. We will 

 endeavor to give a clear account of the constitution of 

 these three kinds of substances, and to mark their place in 

 the register of science. The hydrocarburets are simple 

 combinations of carbon and hydrogen, as, for instance, the 

 petroleum-oils. They represent the simple compounds of 

 organic chemistry. As to aldehydes and ethers, their com- 

 position is rather more complex ; besides carbon and 

 hydrogen, they contain oxygen. Every one knows what 

 chemists mean by an alcohol ; it is a definite combination 



