COMPOSITION OF PLANTS. 79 



that render them fertile when present, and 

 barren when absent, should be the first lesson 

 of the farmer who wishes to be successful in his 

 business and pursue it on a rational basis. 



The methods employed for manuring and 

 cultivating lands vary in different countries, 

 and in different sections of the same country. 

 Certain local circumstances seem to control these 

 differences ; but in most cases they are only the 

 result of custom or ignorance. Hence, if we 

 inquire in what manner manure acts, we are 

 likely to receive the following answer, even 

 from otherwise intelligent men : " Its action is 

 a mystery ; we know that we cannot raise crops 

 without it, and hence we use it in our soils." 

 The excrements of men and animals are supposed 

 by them to contain a mysterious something, 

 which assists the growth of plants, and increases 

 the amount of production ; and the more filthy 

 and unsavory the substance, the more value it 

 is supposed to contain. 



Accurate knowledge of the constituents of 

 different cultivated plants is all important ; we 

 should know what we are going to produce; 

 otherwise how can we work intelligently to 

 produce it. 



All plants cultivated 'for the use of man may 

 be classified as follows : 



I. Potash Plants the ash of which contains 



