CHAP. XVII. 
ODOUBS. 
439 
parts of their secretions experience in escaping through the 
tissue which encloses them, as well as to the degree in which 
the volatile matter may be fixed. Thus resinous woods, such 
as Cedar and Cypress, are fragrant for an indefinite period, 
because the resinous matter in which their odour resides is 
parted with slowly. Parts whose scent resides in essential 
oil preserve their scent for a long time, where the essential 
oil is but slightly volatile, or the wood is thick and hard : 
thus the Rose-wood of Teneriffe (not the Rose-wood of the 
English cabinet-makers), produced by Convolvulus scoparius, 
preserves its odour a very long time ; and, in order to elicit it, 
it is necessary to rub the wood strongly, so as to produce heat 
enough to volatilise the matter which is locked up in the very 
compact tissue of which that plant consists. The necessity 
of producing a little heat, in order to produce an exhalation 
of the volatile matter, is further exemplified by the fragrance 
emitted by many v/oods, otherwise scentless, when exposed to 
the violent friction of a turner’s lathe ; Beech is said to ac- 
quire, under such circumstances, the smell of roses. But 
when, on the other hand, the volatile matter is enclosed in 
wood of a loose texture, neither is heat required to elicit it, 
nor has the wood, if exposed to the air, the power of retaining 
it for any considerable time, for the oxygen of the atmosphere 
will seize upon it rapidly, and quickly leave nothing behind 
but the inodorous tissue : this happens to Cassia and Cin- 
namon. 
Fugitive smells are those which, belonging to perishable 
organs, are either extremely perishable in their very nature, 
or are placed in tissue of the laxest kind, or are situated on 
the surface of plants where their volatile parts are continually 
abstracted by the atmosphere, or finally are secreted in quan- 
tities so small that a short exposure to air suffices to dissipate 
them. All these odours are produced only during the life of a 
plant; they are dispersed as they are formed, and after death 
leave no trace of their existence behind them. Like per- 
manent odours, these are continually given off ; and in some 
plants, as the Orange and the Violet, without any variation in 
intensity in different states of the atmosphere ; but in the 
majority of cases the power of the smell will vary according 
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