PLATE 4 



I, II.— Influence of soil reaction on extent of damage by tobacco rootrot: I, Infested 

 soil; II, tininfested soil — 



lA, infested soil, lime requirement 9.38 tons per acre; 

 2A, infested soil, lime requirement 7.19 tons per acre; 

 3A, infested soil, lime requirement 4.60 tons per acre; 

 4A, infested soil, lime requirement 2.62 tons per acre; 

 SA, infested soil, lime requirement 0.72 ton per acre; 

 6A, infested soil, slightly alkaline; 

 7A, infested soil, strongly alkaline; 

 iB, uninfested soil, lime requirement 9.38 tons per acre; 

 2B, uninfested soil, lime requirement 7.19 tons per acre; 

 3B, uninfested soil, lime requirement 4.60 tons per acre; 

 4B, uninfested soil, lime requirement 2.62 tons per acre; 

 5B, uninfested soil, lime requirement 0.72 ton per acre; 

 6B, uninfested soil, slightly alkaline; 

 7B, uninfested soil, strongly alkaline. 

 Ill, IV.— Influence of the amount of organic matter in the soil on injury by tobacco 

 rootrot: III, 1A-6A, Influence, of gradually increasing amounts of organic matter 

 in infested soil from lA, no organic matter, to 6A, all leaf mold. 

 Planted soon after heavy inoculation. 



IV.— 1B-6B, Influence of gradually increasing amounts of organic matter in unin- 

 fested soil from iB, no organic matter, to 6B, all leaf mold (control series). 

 Planted soon after heavy inoculation. 



V, VI.— Influence of the amount of organic matter in the soil on injury by tobacco 

 rootrot: V, 1A-5A, Influence of gradually increasing amounts of organic matter in 

 uninfested soil from lA, no organic matter, to 5 A, all leaf mold (control series) ; 

 VI, 1B-5B, Influence of gradually increasing amounts of organic matter in infested 

 soil from iB, no organic matter, to 5B, all leaf mold. 

 Planted some months after moderate inoculation. 



