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. [Photograph ~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 



