Effect of Arsenic Com/pounds 



55 



With sodium arsenite the dilutions were carried further, to 

 1/250,000,000, but this still depressed barley to some extent (Fig. 13). 



TohJ 



Shoot' 



l-O 

 1-4. 

 1-2 

 10 



•8 



•6 



■4 



■2 

 O 



SO 10 &e 5 4 2 I -a -I -o^ -oa o 



\ 1-111,000,000 



Fig. 10. Curve showing the mean Ti^lue of the dry weights of ten series of barley plants 

 grown in the presence of arsenions acid and nutrient salts. (March 16th — May 9th, 

 1911.) 



Root 



gm. 

 hO 





Tohol 

 Sho<* 



"rrr^Hoof 



no SO 10 



4 2 I 



I '1:1,000,000 



Fig. 11. Curve showing the mean value of the dry weights of ten series of pea plants 

 grown in the presence of arsenious acid and nutrient salts. (June 8th — July 21st, 

 1910.) 



With peas the results vary somewhat in the different tests, the depres- 

 sion with 1/2,500,000 and less being usually slight, though occasionally 

 it is much more strongly marked (Fig. 14). In a single series with 

 sodium arsenate barley was apparently unaffected by a concentration 



