294 GENERAL MICROBIOLOGY 







13. Repeat, removing a colony to the slice of each of the 

 different vegetables. 



14. Examine in twenty-four hours for evidences of soft 

 rot, and note progress of softening from day to day. What 

 is demonstrated by this phenomenon? Are all vegetables 

 attacked? 



15. What parts of the plant does B. carotovorus attack? 

 What chemical constituents of these parts are decomposed 

 through the agency of their action? 



What are the main features of difference in the mechanism 

 of action of the various types of bacterial plant diseases? 



Give an example of a disease illustrating each. 



How is the progress of infection effected in these various 

 types? What organisms produce a disease of similar type 

 in other vegetables and plants? 



What is known of immunity in the plant kingdom? 



What methods of control are employed with different 

 types of plant diseases? How are methods of control 

 influenced by the type of disease? 



Note. This exercise may be made more interesting and instructive 

 if combined with histological methods. 



Plates illustrating the invasion of root tissues by B. carotovorus 

 are found in Smith's Bacteria in Relation to Plant Diseases, Vol. I, 

 pp. 56, 103. 



16. State in full your results and conclusions. 



REFERENCES 



SMITH, ERWIN F.: Bacteria in Relation to Plant Diseases, Vol. I, 

 pp. 5, 6, 65, 86, 103. Vol. II, pp. 51-52, 65, 81-88, 96, 292. 

 Vol. III. 



MARSHALL: Microbiology, pp. 490-519. 



JONES, L. R.: A soft rot of carrot and other vegetables, pp. 299, 

 13th Rept. of Vt. Expt. Sta. (1901). Also in Cent. f. Bakt. II, 

 Bd. 14, pp. 369-377. 



JONES, L. R.: Pectinase, the cytolytic enzyme produced by B. caroto- 

 vorus and certain other soft-rot organisms. Tech. Bui. 11, N. Y. 

 Agr. Expt. Sta, (1909), 



