PLATE i 
A.—The frosted effect on the surface of the pot is due to mineral nutrients migrating 
through the walls. 
B # —-The illustration on the left shows the effect produced when tomato plants are 
grown in a pot made from acid-proof stoneware containing a sand culture free of 
manganese but with the same quantity and kind of other plant nutrients as the pot 
on the right. ... 
C.—The plants on the left obtained manganese from the pot. Compare with the 
plants on the left in B. 
