186 



VEGETABLE PHYSIOLOGY 



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. 



FIG. 91. PLANTS OF BUCKWHEAT CULTIVATED IN VABIOUS NUTRITIVE 

 SOLUTIONS. 



1, normal solution containing all necessary salts ; 2, solution containing the 

 same salts as 1, except potassium compounds ; 3, 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. 91 shows in (1) a plant growing in such a fluid as is 

 described above ; (2) shows a similar plant cultivated in a 



