170 AMERICAN POMOLOGY. 



we desire to cultivate. Liebig has pointed out how chem- 

 istry may be brought to our assistance in solving such a 

 question. As all the inorganic elements found in a tree 

 and its fruits, must have been derived from the soil in 

 which it grew, he suggested that the ashes of the plant 

 would show us exactly what it needed, and then an exami- 

 nation of the soils would inform us whether they contained 

 all the necessary elements, and in the right proportion. 

 Hence arose the doctrine and the practice of applying 

 special manures, which has been so fashionable in our day. 

 Though there be many doubters as to the efficacy of such 

 investigations and practices, most sensible and enlightened 

 agriculturists admit the truths which Liebig has pro- 

 pounded. 



Light is the great stimulus of vegetation, an essential 

 element to its existence : its withdrawal is followed by an 

 arrest of some of the most important functions of vitality, 

 and yet we find that there is a great difference among dif- 

 ferent species, as to their requirements of this element, 

 and also that various parts and several products of vege- 

 tation require very different degrees of light for their per- 

 fection. It is also found that a sudden exposure of parts 

 from which it had been withheld, is often attended with 

 disastrous consequences. Its withdrawal does not so im- 

 mediately destroy the plant, being attended with the etio- 

 lation of the parts that are usually colored, but a sudden 

 re-exposure to the sun's rays will now destroy the plant. So 

 the removal of a portion of the foliage from a tree, or the 

 exposure of the bare stem of one that had been previously 

 sheltered, is often attended with severe effects, known as 

 sun-scald for which there is no remedy, but very easy 



