PART II. 



PLANTS. 



CHAPTER V. 

 The Plant. 



Constituent Elements of Plants. The plant requires for its 

 nourishment, the same elements as those of which it is composed. 

 It has been determined by analysis that there are ten elements 

 that are absolutely necessary to the development of all vegetables; 

 there are certain other elements utilized by a plant, but they are 

 not indispensable to its life. 



The first ten with their symbols are (C) carbon, (H) hydro- 

 gen, (O) oxygen, (N) nitrogen, (P) phosphorus, (K) potas- 

 sium, (Ca) calcium, (S) sulphur, (Mg) magnesium, (Fe) iron. 



There are usually a few other elements found in the compo- 

 sition of plants, such as silicon, chlorine, and sodium. 



If any of the first ten elements are missing, there is a defect 

 in the plant, and its development will be in proportion to the 

 presence of the element most feebly represented. This is the law 

 of the minimum given by Liebig. 



The plant absorbs the elements by which it is nourished; 

 from the air through its leaves, and from the soil through its 

 roots. Plants obtain from the air all the elements, that escape 

 in the form of gas, from smoke or watery vapor, arising from 

 combustion ; such as carbon, oxygen, hydrogen and a part of 

 nitrogen. They obtain from the soil all those elements that re- 

 main in the ashes after combustion phosphorus, potassium, cal- 

 cium, sulphur, iron, magnesium, and some parts of nitrogen, 

 sodium and silicon. 



Relative Importance of the Different Elements in the Plant. 

 Carbon, oxygen and hydrogen form the bulk of our cultivated 

 plants, but agriculture does not concern itself with these ele- 

 ments for they are furnished directly by air and water. 



It is therefore very important that the student of agricul- 

 ture should know the constituent elements of the soil, that he is 

 to cultivate. Then when he has learned the requirements of the 



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