ODORS. 145 



the sli<»ht volatility of the oil, to which these species owe their 

 [xlors, and the compactness of the wood, enable them con- 

 <»tanllv lo yield their fragrance for an indefinite length of 



time. 



208. Others are fragrant when first cut, but lose this prop. 



crtv in a very short time, as is the case with the Cinnamon 



and Cassia, the fragrant substances being volatile, and the 



>d porous, both causes concurring to render the wood in a 



^iiurt time scentless. 



209 Fugitive odors are such as belong to organs of short 

 duration, as the leaves and flowers, and we meet with them 

 in the greatest abundance, and most frequently in the latter. 

 All are aware, that tho tlower is the source whence llows tiie de- 

 lightlul tVagrance of the fiower garden; and during the season 

 of bloom ol our Magnolias, the woods and swamps are perfumed 

 bv the odor of their flowers. It must have been remarked al- 

 so, bv the most heedless observer, that the odor of the garden, 

 or forest of Magnolias, is much more pungent at some parts 

 of the day, than at others. During the direct action of the 

 mid day sun, little o'r no perfume is percep(il)le from either; 

 but as the sun sinks lo the horizon, and the dews begin to set- 

 tie on the leaves, the evening air becomes scented with their 

 fragrance. The odor accumulates during the night, and as 

 the dew l>egins to exliale with the rising sun, it is borne on the 

 air in much jjreater abundance, than at anv other hour. Thus 

 these silent worshipers pour forth their incense in a morning 

 sacrifice to II im, who extends to them, as to all, his kind re- 

 gards. 



A shower produces similar effects. Who has not enjoyed 

 the gratet'ul odor, exhaled from the flowers of the field or gar- 

 den afier a summer's shower? 



210. The causes of these apparently great emissions of 

 odor, under the circunjstances mentioned, and the apparent 

 suspension of their emission, have not been satisfactorily de- 

 termined. It has been supposed, that the heat of mid dav, un- 

 der the direct action of the sun's rays, produces so much 

 evaporafion, as lo empty, in a great measure, the cells, and that 

 the stomates close, and prevent the emission of the odorous 

 substance ; again, it is tiiought that the excessive evaporation 

 would carry off more of the odors than the plant could gener- 

 ate, and thus the supply lecomes exhausted during tliese hours 

 of heat, and it requires l!je coolness of evenings, when aqueous 

 evaporation is nearly suspended, for the plant to regain its 

 •upply ; but a more probable reason (were we disposed to at- 

 tribute it to any one alone) wo conceive to be, that the exces- 



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