PLATE 67 



I. — Plants illustrating the influence of soil temperature on degree of wilting of 

 plants in soil infested with Fusarium-wilt. The plants were grown at the following 

 soil temperatures: 



iA, i5°to 17 C. 

 2A, iq° to 20 C. 



3 A, 22° tO 2 4 ° C. 



4 A, 26 to 28 C. 

 5 A, 29 to 31 C. 

 6A, 32 to 34 C. 



The upper limit for infection is close to 35 . Infection has occurred at 19 to 20 , 

 but the progress of the disease is very slow. 



II. — Plants grown in the same soil uninfested and at corresponding soil 

 temperatures. 



III. — Plants illustrating the influence of varying soil reaction on the amount of 

 Fusarium-wilt in infested soil. A, highest acidity (medium to strong) to E near 

 neutral and I alkaline end. Same soil (selected for high acidity) in all crocks but 

 brought to various reactions by addition of precipitated calcium carbonate. 



IV. — Plants illustrating varietal differences in resistance of tobacco to Fusarium- 

 wilt. Soil artificially inoculated, uniformly mixed, and transplanted with 20 plants 

 each of the following varieties: A, Connecticut Havana; B, Little Dutch; C, Mary- 

 land Broadleaf; D, White Burley. 



