ILLUSTRATIONS 

 PLATES 



Influence of Son, Environment on the Rootrot op Tobacco 



Page 



Plate i. I. — Influence of amount of infestation on injury from tobacco rootrot: 

 A, All tminfested soil; B, three-fourths iminfested soil; C, one-half unin- 

 fested soil; D, one-fovirth uninfested soil; E, all infested soil. II, III. — 

 Influence of moisture content of soil on the amoirnt of injury done by tlie 

 tobacco rootrot; II, infested soil; III, iminfested soil (control series) — lA, 

 one-fourth saturation infested soil; 2 A, one-half saturation infested soil; 

 3A, three-fourths saturation infested soil; 4A, full saturation infested soil; 

 I B , one-fourth saturation uninfested soil ; 2 B , one-half saturation uninfested 

 soil; 3B, three-fourths saturation uninfested soil; 4B, full saturation unin- 

 fested soil. IV. — Influence of soil temperature on the growth of tobacco in 

 infested soil (jars to left of temperature labels) and in uninfested soil (jars to 

 right of temperatm-e labels) at temperatures of approximately 13°, 17°, 23°, 

 26°, and 36° C ' 86 



Plate 2. I. — Soil temperature tanks used in the temperature experiments. 

 II, III. — Influence of soil temperature on the growth of tobacco: lA, in- 

 fested soil, i7°-i8° C. ; 2A, infested soil, 2o°-2i° C; 3A, infested soil, 23°- 

 24° C; 4A, infested soil, 25°-26° C; 5A, infested soil, 28°-29° C; 6A, 

 infested soil, 3i°-32° C; iB, uninfested soil, i7°-i8° C; 2B, tminfested 

 soil, 2o°-2i° C; 3B, uninfested soil, 23°-24'' C.;4B, iminfested soil, 25°-26° 

 C; 5B, tminfested soil, 28°-29° C; 6B, uninfested soil, 3i°-23° C. IV.— 

 Influence of different soil temperatiueson root development: lA, luiinfested 

 soil, i7°-i8° C; iB, infested soil, i7°-i8° C; 2A, uninfested soil, 2o°-2i° 

 C; ^B, infested soil, 2o°-2i° C; 3A, uninfested soil, 23°-24° C; 3B, in- 

 fested soil, 23^-24° C; 4A, uninfested soil, 2 5°-26° C; 4B, infested soil, 

 25°-26° C; 5A, uninfested soil, 28°-29° C; 5E, infested soil, 28°-29° C; 

 6A, iminfested soil, 3i°-32° C; 6B, infested soil, 3i°-32° C 86 



Plate 3. Influence of high (30° C.) and low (20" C.) soil -temperature on 



recovery of plants in infested soil 86 



Plate 4. I, II. — Influence of soil reaction on extent of damage by tobacco 

 rootrot: I, Infested soil; II, uninfested soil — lA, infested soil, lime require- 

 ment 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; 5A, infested soil, lime require- 

 ment 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, unin- 

 fested 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, tminfested soil, slightly alkaline; 7B, tminfested 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 amotmts of organic matter in infested soil from lA, no organic 

 matter, to 6A, all leaf mold. IV. — 1B-6B, Influence of gradually increasing 

 amounts of organic matter in uninfested siol from iB, no organic matter, to 



(V) 



