44 TOXIC LIMITS OF ALKALI 



where the solution containing the alkali salts was tap 

 water. Tottingham (29) did not find the introduction of 

 potassium chloride or sodium chloride into Knop's solution 

 to have any marked effect on wheat plants, although the 

 sodium chloride depressed the dry weight and length of 

 roots of buckwheat. 



Alkali Solutions. Alkali solutions have been used in 

 a number of different ways to determine toxicity. Some 

 experimenters have germinated the seed in the alkali solu- 

 tions; others have used the alkali solutions in which to 

 immerse the roots of the seedlings after they have germi- 

 nated under normal conditions. Since conditions differ 

 so widely under the two methods and because the time 

 allowed for the alkali to become effective differs consider- 

 ably, the two methods will be treated separately. 



Seed Germination. Experiments with wheat in 

 Wyoming (4, 27) show that salts hinder the absorption 

 of water by the seed so that germination is retarded and 

 that the kind of neutral salt is of less importance than the 

 osmotic pressure of the solution. The work of Kearney 

 and Cameron (14) on antagonism and of the author (10) 

 apparently disprove the latter statement, however. From 

 the Wyoming experiments which included salt solutions 

 from 1000 to 90,000 parts per million in strength, it was 

 found that inhibition was not retarded in as rapid pro- 

 portion as the osmotic pressure of the solution was in- 

 creased. Inhibition was apparently not influenced by the 

 vitality of the seed nor did the salts affect the vitality of 

 the seed when removed before sprouting. The weaker 

 solutions up to 4000 parts per million of sodium sulphate, 

 sodium chloride, magnesium sulphate, or sodium car- 

 bonate had a beneficial effect on the germination of the 

 seed and the growth of the plants. 



