240 THE ROYAL SOCIETY OF CANADA 



The toxic factor here is no doubt the sodium carbonate — prob- 

 ably .2 per cent would represent the limit of sodium carbonate 

 for Vetch and Rye. Further investigation is necessary to supply 

 evidence for a limit of sodium sulphate. 



Of all the series examined magnesium sulphate seemed to occur 

 only in places where sodium sulphate had already reached and 

 exceeded a toxic amount, so that from data accumulated it is impos- 

 sible to draw any inferences about the toxic quality of magnesium 

 sulphate other than that it adds to the general injurious effect of 

 sodium sulphate and sodium carbonate. 



