154 PERSPIRATION OF LEAVES. 



rect, that if the leaves of a tree be stripped off, the fruit 

 comes to nothing, which is exempHfied every year in 

 Gooseberry bushes devoured by caterpillars ; and 

 though the fruit-trees of vi^arm climates, partly natural- 

 ized with us. Grapes and Peaches for instance, ripen 

 their fruit sooner perhaps if partially deprived of their 

 leaves, yet if that practice be carried too far, the fruit 

 perishes, as gardeners who tried it soon discovered. The 

 White Mulberry indeed, cultivated in the south of Eu- 

 rope for the food of silkworms only, bears wonderfully 

 the loss of its foliage three or four times a year. How 

 far the fruit is injured nobody thinks it worth while to 

 inquire, as it is never eaten, but it certainly does not 

 fall off prematurely. 



That Leaves imbibe and give out moisture has been 

 long known, this being one of the most obvious facts 

 belonging to them. Dr. Hales thought they might 

 probably imbibe air ; but since his time more certain 

 discoveries have been made concerning this point, as 

 well as the effect of light upon leaves, which also did 

 not escape the consideration of that great philobopher. 

 All these subjects we shall mention in their turn. 



That Leaves give out moisture, or are organs of in- 

 sensible perspiration, is proved by the simple experi- 

 ment of gathering the leafy branch of a tree, and imme- 

 diately stopping the wound at its base with mastick, wax, 

 or any other fit substance, to prevent the effusion of 

 moisture in that direction. In a very short time the 

 leaves droop, wither and are dried up. If the same 

 branch, pardy faded, though not dead, be placed in a 

 very damp cellar, or immersed in water, the leaves re- 



