140 LEAVES. 



Europe, is said to lose a quantity equal to twice its own 

 weight. On a warm summer'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 wa* 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 us how fast their roots absorb, or 

 their leaves exhale, and in cultivating rare plants, this 

 simple experiment will enable us to determine, what 

 quantity of water they require. But in the perform- 

 ance of this experiment, the condition of the atmos- 

 phere, must be taken into consideration. Nor should 

 it be entirely overlooked by the practical gardener, 

 whose operations frequently fail, because they are 

 performed at an untimely hour. Every person who 

 has been engaged in transplanting, knows it may be ac- 

 complished with more success, on some days than on 

 others. If removed when the air is warm and dry, 

 plants are apt to wither, and unless carefully managed, 

 they will shortly perish beyond the power of recovery : 

 but under different circumstances, and at a proper time, 

 the same thing is performed without difficulty or dan- 

 ger. 



The fluid which is exhaled by the leaves, may be col- 

 lected, by introducing a branch into a capacious glass 

 vessel, but it possesses no very peculiar properties. 

 In all plants it is nearly uniform, being the residue of 

 the s»p, after the separation of its more essentia! secre- 

 tions. Occasionally it is combined with a volatile oil, 

 which communicates to the atmosphere around, the pe- 



