6 



BACTERIA IN RELATION TO PLANT DISEASES. 



In the present state of our knowledge (i) and (2) can usually be considered 

 only after a very careful study of (3), (4), and (5), and of the organism itself. They 

 involve a knowledge of modern languages, and a very considerable familiarity with 

 scientific literature. 



PREVIOUS LITERATURE. 



One of the first requisites in a student is a knowledge of how to use literature. 

 Previous literature is, however, often of such a fragmentary and uncertain sort, as 

 we shall see, that it is impossible to decide whether a disease is actually new or has 

 been written upon before. 



Fig. 3* 



The literature of plant diseases will not be referred to in this volume, except 

 occasionally and incidentally. The bibliography of this volume deals only with 

 general bacteriology human and animal diseases, methods of work, etc. 



*Pic. 3. A detail from fig. 2. Bacillus carotovorus wedging apart cells of the carrot. Drawn 

 -mostly from one plane. In placing the cover-glass a few of the bacteria have been crowded out of 

 the intercellular spaces into .parts they did not originally occupy. X 1,000. 



