PLATE XXI 



Red clover, showing effect of sulphates on growth of roots. A , Check; B, nitrogen, 

 phosphorus, potassium; C, nitrogen, phosphorus, potassium, plus sulphur as sodium 

 sulphate; D, nitrogen, phosphorus, potassium, plus sulphiu" as calcium sulphate; E, 

 sodium sulphate only; F, calcium sulphate only. 



