THE FEEDING FUNCTIONS OF PLANTS. 95 



-culture, consisting of books and periodical journals, sprang 

 into existence, and was eagerly procured and read; and 

 lastly special schools for teaching the science and art of 

 farming were established jointly with farms and laboratories 

 for experimental culture and chemical investigations. Thus 

 step by step the art of growing farm crops became an intelli- 

 gent industry, and farmers are respected in proportion to 

 the importance and dignity of their vocation. 



For all this we are indebted to numerous pains-taking 

 men, who with unusual self-denial, patience, and per- 

 severance, have spent their lives in industrious retirement ; 

 heard of by few and known by less ; busy in their fields 

 and experimental plots, or hidden in their laboratories; 

 gradually building up, fragment by fragment, the grand 

 edifice of knowledge which now represents what every man 

 who desires, may know of the culture of farm crops. 



One very important point of this knowledge is the fact 

 that vegetables feed that is, absorb and assimilate or build 

 up their substance upon mineral substances, as well as up- 

 on the remains of vegetable matter. That while these re- 

 mains in the shape of completely decomposed farm manure, 

 or animal matters, contain the various inorganic compounds 

 which are found in the ashes of plants, and which are 

 known to be, necessary to their growth, yet j;he same com- 

 pounds drawn from a mineral origin, are equally serviceable 

 as plant food. Thus, lime procured from the lime kilns; 

 potash from the rocks of which it forms a part; gypsum or 

 plaster; phosphate of lime; soda in the form of salt, or as 

 nitrate of soda ; sulphate of magnesia; and other mineral 

 substances; when finely ground, and made soluble, produce 

 precisely the same results when used as fertilizers as the 

 same substances in the ashes of plants, or in their decayed 

 remains. They are absorbed by plants with equal facility, 

 and are utilized in the same way and to the same extent, in 

 forming the tissues of the plants. They are in fact plant 

 food. Hence the common idea that these fertilizing sub- 

 stances are stimulants only, and merely encourage the 

 crops to put forth some unusual effort, so to speak, by which 



