New York Agricultural Experiment Station. 39 



(a) Air-Derived Elements. 

 Carbon. 

 Hydrogen. 

 Oxygen. 

 Nitrogen. 



(b) Soil-Derived Elements. 



Phosphorus. 



Sulphur. 



Chlorine. 



Silicon. 



Calcium. 



Iron. 



Potassium. 



Sodium. 



Magnesium. 



Manganese. 



It is nsual among writers on agricultural chemistry to call these 

 classes organic and inorganic elements, but this use of these words 

 is extremely inaccurate ; for any element may be either organic or 

 inorganic, according as it is or is not a part or product of an organ- 

 ized body. Oxygen, as it exists in the air, is inorganic matter ; but 

 when, through vital processes, it becomes part of an animal or plant, 

 it is organic. 



These two classes of elements differ in three important particulars, 

 as follows : 



First. The elements of the first class are derived exclusively from 

 the air, either directly or indirectly ; while those of the second class 

 come exclusively from the soil. 



Second. Air-derived elements disappear, for the most part, in the 

 form of gases, when a plant is burned ; while the soil-derived ele- 

 ments, usually the smaller part, are left in the form of a residue or 

 ash, upon which further heating will not have any effect. Some 

 carbon and oxygen and nitrogen are always found in the ash, while 

 slight quantities of chlorine, sulphur and phosphorus are apt to be 

 driven off by heating. The two classes of elements are, therefore, 

 not so shai'ply defined in this regard as they are in respect to the 

 sources from which they come. 



Third. These two classes differ very noticeably in regard to the 

 quantities in which they are present in plants. Thus, the air-derived 

 elements constitute, at least, ninety-Jive per cent of the whole veg- 

 etable hingdojn, while the soil-derived elements occur in small quan- 

 tities, varying from a fraction of one per cent up to ten per cent., or 

 even more in some cases. Because the soil-derived elements occur 



