Amount of Alkali Injurious 



277 



Sodium nitrate is also given in these cases as a 

 constituent, but as this may be regarded as a plant- 

 food, we have omitted it from the table. It will be 

 observed that the total soluble salts in the surface 3 

 inches where the barley grew well was about half that 

 found in the case where it would not grow, the amounts 

 in the two cases being 1.2 and 2.44 per cent of the soil. 

 The difference between the amounts of the black alkali 

 in the two cases stands as 8 to 70, or much more. 



Referring to the possibility of these salts interfering 

 with plant life simply on account of their plasmolitic 

 action, it may be said that DeVries found, as repre- 

 sented in Fig. 49, that when the living cells of a plant 

 were immersed in a 4 per cent solution of potassium 



1234 



Fig. 49. Effect of too strong solution of potassium nitrate on the 

 protoplasm of plant cells. (After De Vries.) 



nitrate, there was first a shrinkage in volume through 

 a loss of water, as shown between 1 and 2. When 

 the solution was given a strength of 6 per cent, then, 

 in addition to the change in volume, the protoplasmic 

 lining P began to shrink away from the cell wall h, 

 as shown at 3, and when the strength of the solution 

 was made 10 per cent, the conditions shown in 4 were 



