50 



ON INCREASING THE GROWTH 



this ingredient. From gypsum, plants may provide 

 themselves with lime and sulphur ; but it will only 

 act beneficially in such soils as are destitute of both 

 these substances, or at least of one of them. In 

 bone-dust the principal constituents are nitrogen, 

 lime, and phosphorus ; when, therefore, it is placed 

 upon a soil in which these elements are already 

 present in sufficient quantity, it will be of little or no 

 efficacy ; whereas in a soil poor in only one of these 

 constituents, it may produce remarkable effects. 



To this it must be added, that all plants which we 

 cultivate do not require for their nourishment an 

 equal quantity of individual substances, more partic- 

 ularly of such as are inorganic or mineral. Thus, 

 for example, the following quantities were found to 

 be about those which are necessary to produce 

 1,000 lbs. of each of the under-mentioned articles of 

 produce : — 



Hence it is apparent, that, to produce an equal 

 weight of each plant, very different quantities of pot- 

 ash, lime, etc. are necessary, and from this it obvi- 



