Plate 12. — Apricot seedling grown in nutrient 

 solution in pyrex vessel, under zinc deficiency con- 

 dition. Zinc deficiency symptoms were similar in 

 several respects to those shown by seedlings grow- 

 ing in soil producing the little-leaf disease. (From 

 HoAGLAND, Chandler and Hibbard, 1936). 



