CONDITIONS FOR THE GROWTH OF PLANTS. 27 



high tropical mountain, the same differences in 

 the variety and luxuriance of plant life are noticed 

 that are seen in going from the equator to the 

 poles. This is due mainly to the distribution of 

 the heat and moisture. 



The planting of a germ or seed in any soil will 

 not result in its continued growth, unless the con- 

 ditions of heat, light, and moisture are practically 

 the same as those in which the plant from which 

 such germ or seed was derived required for its 

 existence. 



Trees planted in a particular locality may, there- 

 fore, fail to grow in such locality, from want of 

 the proper conditions of heat, light, and moisture. 



In all regions where forests can grow naturally, 

 wherever practicable, they should be permitted to 

 grow, since, as will be shown, the continued ex- 

 istence of forests on certain portions of the earth 

 is necessary for insuring that balance of nature on 

 which the comfortable existence of man depends. 



Guyot, on page 188 in his " Earth and Man," * 



* " The Earth and Man," lecture on Comparative Physi- 

 cal Geography in its Relation to the History of Mankind, by 

 Arnold Guyot, Professor of Physical Geography and History 

 at Neufchatel, Switzerland. Boston : Gould, Kendall & Lin- 

 coln, 1849. 



