144 ODORS. 



sion of functions, of the organs of nutrition. This point he 

 strengthens by the consideration, that the puncture of an in- 

 sect will cause an organ to pass through all the steps to ma- 

 turity, giving all the hues belonging to its species, whether of 

 fruit or leaves. Also, the cold of autumn and winter, produ. 

 ces a similar derangement ; although the agent is different, 

 yet the result is the same. Many ever green leaves become 

 tinored with red in winter, from the influence of cold, but with 

 the return of summer, assume their accustomed greenness; 

 also, the leaves of the extremities of the branches being 

 most exposed to atmospheric influences are changed to red, 

 while those nearer the trunk continue green. If one half of a 

 leaf be protected from the cold, it will remain green while the 

 other half will change to red. But in the case of fruit, heat 

 is the agent, in producing similar effects to those above 

 ascribed to mechanical injury and cold. 



Section .11 Odors, 



206. Much of the importance attached to flowers by peo- 

 ple, generally, is owing to the odors they exhale. The rose 

 has long been cultivated by amateurs, no less for its grateful 

 fragrance, than for its beauties of form and color ; and those, 

 which combine these properties, are the most favored objects 

 of the Florist's care. The cause of the odors of Plants, is no 

 doubt, the disengagement of a volatile oil, which, in some ca- 

 ses is easily obtained, and made subservient to the use of man, 

 in others it entirely eludes every effort, to confine or preserve 

 it, being as evanescent as the light, which is the agent of its 

 production. 



207. Odors are distinguished into permanent, fvgiiivef and 

 inter mittenl, Permanent odors are such, as are enclosed in 

 the tissues of \^\\q wood and bark of plants, in a concentrated 

 form ; and either from being but slightly volatile, or contained 

 in close vesicles, which prevent exhalation, they remain for 

 a long time, giving to the organs in which they are contained 

 their peculiar odor. There is probably no part of a vegetable 

 absolutely destitute of permanent odor. Every variety of 

 wood, under certain circumstances, exhibits it. Some, nearly 

 scentless otherwise, become strongly odorous, when rubbed 

 or heated. The Pine, Oak and Beech, are examples of this 

 kind. Others are odorous for a long time after being cut, un- 

 der ordinary circumstances ; of this kind, are the Rosewood of 



• Teneriffe, the Cedar and Sandal wood (Santalum Album) of 

 India, so highly esteemed in Eastern Asia for its fragrance. 



