64 



EXPERIMENT STATION. 



[Jan. 



disappeared in a few weeks. No. 5 was treated with a com- 

 mercial arsenite of soda, and No. 8 was only one-third as strong 

 as No. 7. These tests show that the arsenic compounds are 

 many times more effective than any of the other substances em- 

 ployed. The carbolic acid gave the quickest results, but this 

 substance appears to affect merely the foliage of the plant. In 

 some cases this treatment is all that is necessary to destroy 

 weeds, while in others it is of little value. 



Salt as a weed killer loses some of its reputed efficiency when 

 compared with the arsenic compounds ; nevertheless it is ca- 

 pable of injuring vegetation, as may be seen where large quan- 

 tities are applied to electric railroad beds in the winter to clear 

 the tracks, or to sidewalks to help in removing the ice. There 

 are instances of valuable shade trees being injured by the ap- 

 plication of salt, and even the salt-water drainage from dairies, 

 when allowed to j)ass close to trees, has been known to destroy 

 their roots. Salt is not, however, very toxic to most plants, 

 and its principal 'action consists in plasmolysing the cell. If 

 applied at all it should be put on in hot, dry weather. 



The series of experiments shown in Table II. was conducted 

 in the same general way, but different chemicals were employed. 

 The observations recorded were made at different periods for 

 two months. 



Table II. — Showing the Effects of Chemicals upon Vegetation. 



