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OBSEKVATIONS ON THE FUNCTION OF THE ETHEKEAL. 

 OILS OF XEEOPHYTIC PLANTS. 



By E. Maeloth, Ph.D. 

 (Bead March 30, 1906.) 



It is well known that aromatic substances are widely distributed 

 in the vegetable kingdom, for they occur in roots as well as in stems,, 

 leaves, and flowers. The scents of flowers evidently serve other 

 purposes than those of the vegetative organs, for they act as an 

 attraction to insects, which assist the plants in the process o£ 

 pollination. Especially nocturnal insects are guided in this way to' 

 the nectar stored for them in the flowers, and it is for this reason 

 that many flowers exhale their sweet perfumes only at night- 

 time. 



My remarks shall be confined, however, to another class of 

 ethereal ■ oils, viz., those occurring in the leaves of plants. They 

 are found in almost every natural order, and in some of them 

 their occurrence is universal. Consequently the function of these 

 essential oils has been often discussed, although few experiments 

 only have been made to ascertain their use. 



In the earlier part of the last century these oils were often looked 

 upon as mere waste products or excretions, which had to be removed 

 from the body of the plant not only as useless but even as injurious 

 to its own well-being. In modern times two views are held with 

 regard to their function. One regards these aromatic substances as 

 means of protection of the plants against animals, which are thereby 

 deterred from feeding upon them. There can be no doubt that in 

 many cases protection is obtained in this way, not only against 

 grazing animals but especially also against the attacks by larvae of 

 insects, such as butterflies or moths, and the snails and slugs. 



One has to distinguish, however, between plants that possess 

 special internal reservoirs for storing the essential oil within their 



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