THE CONSTITUENTS OF THE ASH OF PLANTS 173 
the plants injuriously. Too great a quantity of salts, 
however, becomes deleterious. 
The effect of omitting any particular constituent can 
be examined by making up the culture-fluid as required. 
. 
Fic, 89.—Puanrs or BUCKWHEAT CULTIVATED IN VARIOUS NUTRITIVE 
SoLUTIONS. 
1, normal solution containing all necessary salts; 2, solution containing the 
same salts as 1, except potassium compounds; 8, solution of same composi- 
tion as 1, except that sodium salts have been substituted for potassium 
compounds; 4, solution of same composition as 1, except that no calcium 
salts are present; 5, solution containing no compounds of nitrogen. 
Fig. 89 shows in (1) a plant growing in such a fluid as is 
described above; (2) shows a similar plant cultivated in a 
