Relation to Deleterious Chemical Agents 455 



279. Deleterious substances employed. - - Common salt 

 is only slightly toxic, yet it has been much employed on 



FIG. 130. Greater ragweed in untreated field of wheat. [Photograpli by 



H. L. Bolley.] 



account of its osmotic action. It may be used dry in 

 roadways and other situations, and it has sometimes been 

 effective in suppressing broad-leaved, delicate weeds in 



