PREFACE vii 



entific method as a tool, and independent thinking 

 as well. The fact that scientific work progresses 

 more rapidly when consciously pursued than other- 

 wise should serve as ample justification for this 

 emphasis. 



A word of explanation is desirable to explain cer- 

 tain features of this volume. It is the outcome of 

 cooperative work on the part of the Illinois State 

 Laboratory of Natural History and certain members 

 of the Ecological Survey Committee of the Illinois 

 Academy of Science, Professors E. N. Transeau and 

 T. L. Hankinson. A local ecological study was 

 made, as a piece of cooperative work, and directions 

 for study were to be an introductory section of my 

 part of this report. But as this part grew on my 

 hands, with the permission of Professor S. A. Forbes, 

 Director of the Illinois State Laboratory of Natural 

 History, I decided to publish it separately. This 

 part was written two years and a half ago, and when 

 separate publication was decided upon, additional 

 references to the literature were added to bring it 

 to date. These circumstances explain the emphasis 

 placed upon ecological surveying and also the brevity 

 of treatment of other aspects. 



Further, I am indebted to Professor Forbes for 

 reading the manuscript and for valuable criticisms, 

 and likewise, for similar assistance, to my wife, Alice 

 Norton Adams. Skillful help on the proof and index 

 has been given by Miss Marion E. Sparks. 



CHAELES C. ADAMS. 

 URBANA, ILL., U.S.A., 

 June 9, 1913. 



