IDEAL FERTILIZERS 59 



trate the sap in these areas, therefore, the osmotic move- 

 ment is (under normal conditions) ever upward. Plants 

 vary, but it is estimated that they average to lift three 

 hundred twenty-five pounds water for every pound of 

 dry matter grown. Now, since the soil water must 

 enter the plants with its varied solutions, it would 

 seem that there were danger of harmful accumulation 

 of matter not used by the plant, but here is where diffu- 

 sion comes to the rescue. I will quote from King : "The 

 loss of water by evaporation through the surface of the 

 plant or the consumption of it as food, which tends to 

 make the strength of the solution of those substances not 

 used as food stronger, cannot result in a permanent in- 

 crease of them in the plant, because, unless these sub- 

 stances are actually taken out of solution, they travel 

 back toward the roots again and escape into the soil 

 water so long as the solution inside is stronger than is 

 that outside." 



Perhaps further distinction should be made between 

 plants using and needing different elements. Certain 

 elements named under the heading "Plant Constituents" 

 are needed because the plant cannot grow without them. 

 Other elements chlorine, silicon and sodium, the first 

 two forming acids and the last being a base are in- 

 variably found in plants grown under normal conditions ; 

 and still other elements such as manganese sometimes 

 occur. These last elements are used but are not needed, 

 as the plant could grow equally well without them. 



