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atmosphere is charged with moisture, a condition hostile to the ordinary 

 hypothesis that the fragrance of plants is dependent upon the evolu- 

 tion of certain volatile oils, upon which the perfume depends, for the 

 presence of water in the air is certainly calculated to prevent rather 

 than accelerate the transmission of particles of oil. Again, if the per- 

 fume of plants depended upon the evolution of volatile atoms, that 

 perfume would only exist as long as the life of the plant cells con- 

 tinued, or at aU events its effect would be much diminished upon the 

 death of the plant ; such however, is not always the case, — the delicate 

 rose, the pungent labiate plants, and a hundred others, retain their 

 power of perfume after the death of the tissue which yields it ; and 

 strange to say, in some instances, as in the woodrufi', (Asperula odorata), 

 the perfume is only eliminated after death. 



From these, and a multitude of instances of a similar kind, I am led 

 to this conclusion : — That the combination of oxygen with certain secre- 

 tions of plants, leads, both in life and death, to a peculiar variety of 

 eremacausis or oxidation, the effects of which are transmitted to the brain 

 through the conducting medium of tlie air ; and that a certain quantity of 

 moisture in the air renders it a better conductor of this chemical action. 

 But it will be said, we know that in some cases the result is solely 

 attributable to the volatilization of essential oils. Witness the rinds of 

 the various Aurantiacim, the Menthas, and other labiates, and a great 

 variety of plants, the essential or volatile oils of which are procured in 

 consequence of their odour. It is true that a substance may be smelled 

 at a distance in consequence of its volatile particles being brought in 

 contact with the olfactory organs, but tliis does not prove the absolute 

 necessity of a constant elimination of atoms from odorous substances ; 

 it simply proves that some subtsances require to be nearer to the nose 

 than others, in order that the sensation may be experienced. Perhaps 

 I am not sufficiently clear upon this point, but let me compare the 

 sense of taste with that of smell ; it is not contended that any sub- 

 stance taken into the mouth is brought into absolute contact with the 

 nerves of taste, but the sensation is communicated or conducted through 

 the skin of the tongue, as that of feeUng is also conducted by the skin 

 of the fingers. 



My theory is, that this power of conduction may also be extended to 

 that portion of the atmosphere which intervenes between the plant cell 

 and the olfactory membrane ; or else that the intervening atmosphere 

 itself undergoes an absolute chemical change by its contact with the 

 active oxygenization going on in the plant cell ; and this chemical 

 change may be extended for a considerable space. In support of this 



