VIII Journal of Agricultural Research voi. xiii 



Some Bacterial Diseases of Lettuce 



Page 



Plate E. i. — Bacterium viridilividutn, second organism isolated from Virginia 

 lettuce : Appearance of the growth on potato at the end of 2 days. 2 . — Bac- 

 terium viridilividum., original organism from Louisiana: Appearance of the 

 growth on potato at the end of 2 days. 3. — Bacterium viiians, first organism 

 isolated from Virginia lettuce: Appearance of the growth on potato at the 

 end of 2 days. 4. — Bacterium viiians, isolated from South Carolina lettuce: 

 Appearance of the gro\vth on potato at the end of 3 days. 5. — Bacterium 

 m.arginale, isolated from Kansas lettuce: Appearance of the gro-wth on 

 potato at the end of 2 days. 6. — Bacterium, marginale, isolated from Kansas 

 lettuce: Appearance of the growth on potato at the end of 13 days 388 



Plate 29. Bacterium vitians: A. — Lettuce from Beairfort, S. C, showing stems 

 blackened by the disease. B. — Lettuce leaves from South Carolina, show- 

 ing spotted-leaf type of the disease 388 



Plate 30. Bacterium vitians: A. — A field of 3^-^ acres of diseased lettuce at 



Beaufort, S. C. B.— A field of healthy lettuce at Beaufort, S. C 388 



Plate 31. Two badly diseased leaves of Virginia lettuce, from which both 

 Bacterium, viridilividum and the South Carolina yellow organism Bad. 

 vitians were isolated 388 



Plate 32, Bacterium viridilividum,, the cause of the Louisiana lettuce disease: 

 A. — Three leaves of lettuce inoculated by needle pricks on February 15, 

 1915. B. — Two pots of lettuce inoculated by spraying on February 19, 



191S 388 



Plate Z2>- Bacterium marginale, the cause of the Kansas lettuce disease: A. — 

 A head of diseased lettuce from Manhattan, Kans. B. — Single leaves of 

 Manhattan lettuce, showing the effect of the marginal disease 388 



Plate 34. Bacterium, marginale: A diseased leaf of lettuce received from Hutch- 

 inson, Kans 388 



Plate 35. A. — Louisiana lettuce disease: Surface colonies on agar-poured 

 plates of Bacterium viridilividum, showing the mottled type of colonies, and 

 also one buried colony. B. — Bact. viridilividum,: Nonmottled type 3 

 days after pouring. C. — Bact. vitians, cause of the South Carolina lettuce 

 disease: Agar-poured plate showing surface, buried, and bottom colonies. 

 D. — Bact. viridilividum, cause of a Virginia lettuce disease: Mottled colo- 

 nies on agar-poured plates. E. — Bact. marginale, cause of the Kansas let- 

 tuce disease: Colonies on surface of agar-poured plates 388 



Plate 36. Bacterium vitians the cause of the South Carolina lettuce disease: 

 A. — Cross-sections of a lettuce stem at two levels 35 days after inoculation 

 Avith the South Carolina yellow organism. B. — A longitudinal section of 

 another plant inoculated at the same time as A. C. — A longitudinal sec- 

 tion of a healthy stem for comparison. D. — Longitudinal sections at the 

 crown of a lettuce plant one month after inoculation, showing bro\vning of 

 the tissues. E. — A cross section at the crown of a lettuce plant one month 

 after inoculation, showing browning of the tissues 388 



Plate 37. A. — Two leaves of a lettuce plant inoculated by spraying with Bac- 

 terium viridilividum isolated from Virginia lettuce. B. — Cross sections of 

 stems of lettuce plants inoculated with the Virginia yellow organism {Bact. 

 vitians), which is the same as the South Carolina lettuce organism 388 



Plate 38. Bacterium viiians: A. — A lettuce plant inoculated by spraying with 

 the Virginia yellow organism, which is the same as the South Carolina yellow 

 organism. B. — Part of a healthy plant for comparison 388 



