28 HANDY-BOOK OF HUSBANDRY. 



These proportions vary somewhat in different analyses, but not 

 materially. Such of these substances as exist in the air are taken into 

 the plant by the leaves, or, having been carried to the soil, by rains, 

 (or added to it by manure, or by the decay of vegetable matter,) 

 through the roots. The ashes are taken directly from the soil. 

 The manner in which they are taken, and the sources from which 

 they are taken most readily, will be discussed hereafter. What I 

 desire to especially emphasize in this connection is the fact, that 

 by far the larger part of all plants comes originally from an atmo- 

 spheric source, and that only a small percentage of their constitu- 

 ent parts is supplied by the mineral portion of the soil. 



THE PLANT AND ITS FOOD. 



The cultivated plant has two sets of feeding apparatus : the 

 leaves and green stems, and the roots. The leaves and green 

 stems absorb carbonic acid from the air, and the roots absorb from 

 the soil the mineral matters^ am?nonia^ and carbonic acid. Within 

 the organs of the living plant such changes take place as are 

 necessary to separate these different compounds, to reject what is 

 not needed, and to assign to its proper place in the organism each 

 element that is to be retained. These changes take place without 

 our aid, are beyond our control, and are therefore, in a practical 

 point of view, not necessary to be discussed here. 



In red clover hay fully ninety per cent., — and in all other prod- 

 ucts about the same proportion, — of the dry weight consists of 

 carbon^ oxygen^ and hydrogen^ which are always abundantly sup- 

 plied to the plant by the decomposition of carbonic acid and 

 water. Of the ashes, certain ingredients, as magnesia., silica^ 

 sulphuric acid., oxide of iron., chlorine., soda., the oxide of man- 

 ganese^ and generally lime.^ are either found in all arable soils in 



they need in no way affect the practices of the farmer. The word " ammonia" is used 

 here (in accordance with a common though not strictly scientific usage) to designate 

 those nitrogenouscompounds which under certain circumstances may assume the form of 

 ammonia. 



