Bui. 82, U. S. Dept. of Agriculture. 



Plate I. 



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Various Stages in the Life History of the Fungus which Causes 

 Powdery Scab. 



A, A large host cell in which there are three amcebse of Spongospora. B, A young host 

 cell in the early stages of infection. The amoeba lies just below the nucleus. C, The 

 amcebEe are coalescing to form the Plasmodium. U, The plasmodial stage. E, Mature 

 spore balls in an enlarged host cell. (A to E, after Osborn.) F, The isolated spore 

 balls photographed. Note the variation. (Original.) 



