/l/ Classified as: high = syn^jtoms seldom occur outside the stated pH; nedium = symptoms occur nost com- 

 monly within the stated pH; low = synqjtoms occur at nil pH values. /2/ Species most sensitive to a toxi- 

 city state and therefore exhibiting synqptoma of excess of the given element in a short period of tine. 

 /3/ Reported to occur in oats from the presence of minerals containing arsenic In the soil, /h/ Incon- 

 sistent results with field plants. 



173 



