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THE FARMER AT HOME. 343 



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regard its subserviency to the wants of the httman race, it is not sur- 

 prising that by the ancients, the wide spreading tree, decorated with 

 leaves, and occasionally beautified with flowers, shou.d have been 

 held sacred as the very temple of the deities they worshipped. 



It has long been known that leaves are organs of exhalation, from 

 which an invisible vapor continually escapes, capable of being col- 

 lected, condensed, and accurately examined. The fact is illustrated 

 by a very simple experiment, and we all know that when a branch 

 is separated from its parent stock, it will shortly droop, wither and 

 die. Its weight is diminished, for it is no longer filled with those 

 fluids on which its firmness and elasticity depend. They have been 

 discharged through the pores of the leaves, which, being cut off from 

 all further supply, are sooner or later entirely exhausted. But if a 

 leafy stem be placed in a small vessel of water, its freshness will be 

 preserved a much longer time, though the perceptible and rapid dim- 

 inution of the water will prove that the leaves have been the outlet 

 through which it has escaped. If the same branch be placed in a 

 close tin box, its freshness will be still longer preserved. Here are 

 no fluids for the stem to absorb, but by confining the air which is al- 

 ready saturated with vapor, we prevent its further escape from the 

 leaves, which must of necessity cease to transpire. They retain the 

 same fluids with which they are already supplied, and though they 

 perform none of the actions, they exhibit the appearance of perfect 

 health. Thus they may be preserved for weeks, and thus the botan- 

 ical traveller, who expects to derive every advantage from his journey, 

 will collect and preserve the plants that meet his eye, till he has 

 leisure to examine them. 



In general, succulent plants exhale more sparingly than others. 

 It seems to have been the design of Nature that they should inhabit 

 the burning sands of the torrid zone, and the peculiarity of their native 

 situation, makes it necessary for them to preserve the fluids, which 

 with so much difficulty they procure. But plants with thin mem- 

 branaceous leaves, which generally occupy moist situations, where 

 they are supplied with an abundance of water, perspire very copiously. 

 The sunflower, which is very frequently met with in the United 

 States, was found to exhale two pounds in the course of a day ; arid 

 in the same space of time the cornelian cherry, a shrub with thin and 

 almost transparent leaves, growing in the hedges of Europe, is said 

 to lose a quantity equal to twice its own weight. On a warm sum- 

 mer's day, at a time when there had been no rain for several weeks, 

 Dr. Watson placed some grass under a large vessel, and in two min- 

 utes it was covered with moisture which ran down its sides. By 

 collecting it on muslin, he ascertained the amount of this exhalation ; 

 and from the result of his experiments, he was led to conclude, that 

 in the course of a day, an acre of land transpires nearly two thousand 

 gallons of water. The rapidity with which plants wither, will teach 



