Smithsonian Report. 1933. — Hurd-Karrer 



1. Plants in nutrient solutions containing 10 p. p. m. sulphate sulphur injured by 1 p. p. m. selenium. 



2. Plants in nutrient solutions eontainin^ 32 p. p. m. suliihate sulphur uninjureil by 2 p. p. m. .selenium, 



injured by 3 p. p. m. selenium. 



3. Plants in nutrient solutions conlainiu'/ 192 p. p. m. sulphate sulphur uninjured (except for slight stunting 

 from excess sulphur) by Ifj p. p. m. selenium, injured by 18 p. p. m. selenium. 



Demonstration of a Critical Selenium-Sulphur Ratio with Wheat Plants 

 Grown in nutrient Solutions Containing 10, 32. and 192 p. p. m. Sulphur 

 AS Magnesium and Ammonium Sulphates, and Various Selenium Con- 

 centrations. 



Figures under flasks denote parts per million selenium as sodium selenate. 



