Bui. 1256, U. S. Dept. of Agriculture 



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Fig. I. — A Parasitic Fungus Growing from Pieces of Tobacco Stalks 



Most plant diseases are caused by organisms of this type 



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i-ig. 2. — Bacteria from Diseased Tobacco 



Many of the diseases of tobacco are caused by these extremely small organisms, visible only when 

 greatly enlarged under the microscope 



