Photo, i. — Acer rvibrum ; FeSO^, m/56 ; three days in solution; veins blackened. 

 Veins blackened to points equally distant from the margin. Area affected symnietricril 

 to whole leaf. 



Photo. 2. — Primula obconica ; FeSO^; 

 m/56 ; blackening of the veins not com- 

 plete. E, utmost limit of the darkening 

 of the veins. 



Photo. 3, — Primula obconica ; FeSO^ ; 

 m/56 ; complete blackening of the veins 

 even to the very minute terminations. 

 Almost no diffusion of the salt away from 

 the veins. 



