THE ATMOSPHKKE AS TIELaTED TO VEGETATION. lOfi 



other in penetrating it. In case a meniLrane is moistened 

 with water or other liquid, or by a solution of solid mat- 

 ters, this would still further modify tlie I'csult. 



Absorption of (Jases by the Plant.— A few words will 

 now suffice to ."ippiy tliese ficts to the abs()r[)tion of the 

 nutritive gases by vegetation. The foliage of plants is 

 freely permeable to gases, as has been set forth in " How 

 Crops Grow,'' p. 289. The eells, or some portions of their 

 contents, absorb or condense carbonic acid and ammonia 

 in a similar way, or at least with tlie same effect, as potash 

 absorbs carbonic acid. As rapidly as tliese bodies are 

 removed from the atmosphere surrounding or occupying 

 the cells, they are re-supplied by diifusion from without ; 

 so that although the quantities of gaseous plant-food con- 

 tained in the air nre, relatively considered, very small, 

 they are by this grand natural law made to flow in con- 

 tinuous streams toward every growing vegetable cell. 



