112 HOW CROPS GEOW. 



In the subjoined table, the names of the 12 elements of 

 the ash of plants are given, and they are grouped under 

 two heads, the non-^metals and the metals, by reason of an 

 important distinction in their chemical nature. 



ELEMENTS OP THE ASH OF PLANTS. 



Nbn-Metah. Metals. 



Oxygen Potassium 



Carbon Sodium 

 Sulphur ■ Calcium 



Phosphorus Magnesium 



Silicon Iron 



Chlorine Manganese 



If to the above be added 



Hydrogen and Nitrogen 

 the list includes aU the elementary substances that belong 

 to agricultural vegetation. 



Hydrogen is never an ingredient of the perfectly burned 

 and dry ash of any plant. 



Nitrogen may remain in the ash under certain conditions 

 in the form of a Oyanide, (compound of Carbon and Ni- 

 trogen,) as will be noticed hereafter. 



Besides the above, certain other elements are found, either occa.sion- 

 ally in common plants, or in some particular kind of vegetation : these 

 are Iodine, Bromine, Fluorine, Titanium, Arsenic, Lithium, Eubidinm, 

 Barium, Aluminum, Zinc, Copper. 



We may now complete our study of the Composition 

 of the Plant by attending to a description of those ele- 

 ments that are peculiar to the ash, and of those compounds 

 which may occur in it. 



It wiU be convenient also to describe in this section 

 some substances, which, although not ingredients of the 

 ash, may exist in the plant, or are otherwise important to 

 be considered. 



The non-metallic elements, which we shall first no- 

 tice, though differing more or less widely among them- 

 selves, have one point of resemblance, viz., they and their 

 compounds with each other have acid properties, i. e. they 



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