PREFACE TO SECOND EDITION. 



Since the publication of the first edition of this work advance 

 along all lines of bacteriology has been very rapid. Scarcely a 

 phase of the relation of bacteria to agriculture has failed to receive 

 substantial contributions. Much new information has been 

 obtained, the relative importance of different subjects has been 

 changed, and in a few points our previous conclusions have been 

 corrected. These changes have been so considerable that in 

 preparing this second edition it has been found necessary to rewrite 

 the whole book in order to bring it up to the times. The subject has 

 grown so large that it is difficult to include within the limits of one 

 volume even the fundamental facts of the rapidly growing science, 

 and many subjects of importance have been treated very briefly. 



The growing recognition of the importance of the subject to 

 students of agriculture has caused agricultural schools and col- 

 leges to give to it an increasing amount of attention. For this 

 reason this edition has been planned with special reference to its 

 use by classes; and some changes in method of presentation have 

 been adopted in order to make it more useful to students. For 

 the same reason there has been added a somewhat extended set of 

 experiments for elementary laboratory work. These laboratory 

 directions are far from exhaustive and are designed simply to intro- 

 duce the student to the methods of bacteriological work. 



The close relation of the functions of the higher fungi to the 

 functions of bacteria has come to be fully realized to-day and has 

 made it necessary to include more extended references to the higher 

 fungi in this review. The only other important addition in this 



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