BENEFITS OF CULTIVATION. 57 



The same seems to be true of all the animals which 

 are subject to man. Their most valuable qualities have 

 been, in a great degree, produced by the intelligent care 

 of men. The same is true of man himself. Children 

 suffered to remain uncared for and neglected, left to 

 themselves, are likely to grow up in a condition little 

 better than that of savages. 



CHAPTER VII. 



ELEMENTS OF PLANTS. 



201. The chemists have found, by careful examination, 

 with the help of the microscope, that plant-cells are never 

 formed except in a fluid containing oxygen, carbon, 

 hydrogen and nitrogen. These then are the elements of 

 which all parts of all plants are composed. 



Of these, oxygen and carbon are obtained from car 

 bonic acid, and hydrogen and nitrogen from ammonia ; 

 and both carbonic acid and ammonia are always found 

 in the atmosphere, and are taken in by the leaves, or are 

 dissolved by the rain falling through the air, and carried 

 into the earth, where they are absorbed by the soil, and 

 hence taken up by the roots. 



It may also be tha t the oxygen and hydrogen are 

 furnished by water, and nitrogen as well as oxygen by 

 the nitric acid sometimes found in the air, and dissolved 

 and brought down by rain. 



202. The simplest plant, consisting of only a single 

 cell, must have the power of decomposing carbonic acid, 

 ammonia, nitric acid, and perhaps water. 



