NOURISHMENT OF PLANTS. 31 



always require certain mineral substances, in addi- 

 tion to the organic, for their nourishment and com- 

 plete development, and that they are obstructed in 

 their growth when they do not obtain a sufficient 

 supply of them. Accordingly, we must regard the 

 ashy constituents in like manner as necessary ele- 

 ments of plants. 



How greatly these inorganic constituents differ, 

 not only in different plants, but even in the different 

 parts of one and the same plant, and also how 

 greatly they vary at different seasons of the year in 

 quantity and quality, may be learned from the fol- 

 lowing table, in which these elements are compared 

 as they exist in certain vegetable ashes. 



In a dried state, 



Of which were 

 Yielded soluble in water : 



100 lbs. of Grains of Wheat, . . 2 to 3 lbs. of ashes, i 

 " « Wheat-straw, . . 4 " 5 '' « \ 



If we inquire what is the constitution of the 

 mineral constituents of plants, chemical analysis re- 



