vi CHAIRMAN'S PREFACE 



and also increased the interest in the project. The American Society of 

 Zoologists and the Botanical Society of America contributed $25.00 each 

 toward the classification of areas as to degree of modification from the 

 original condition. 



The establishment of cooperation with the United States Forest Service 

 greatly reduced our financial and clerical burdens. 



Acknowledgments are due the following institutions for encouraging 

 their staff members in editing or contributing to the work: United States 

 Forest Service; United States Biological Survey; University of Michigan 

 Museum; University of Illinois, Department of Zoology and Natural 

 History Survey; University of Cincinnati, Department of Botany; Oberlin 

 College, Department of Ecology; Northwestern University, Department of 

 Botany; New Hampshire College, Department of Zoology; and the Car- 

 negie Institution. 



The following rendered important service in reading and correcting 

 manuscripts: 



H. A. Gleason, New York Botanic Garden 



H. Burrington Baker, University of Pennsylvania 



A. H. Wright, Cornell University 



C. C. Hamilton, University of Maryland 



Vernon Bailey, U. S. Biological Survey 



P. L. Kicker, U. S. Bureau of Plant Industry 



A. H. Howell, U. S. Biological Survey 



W. L. McAtee, U. S. Biological Survey 



H. P. Loding, Mobile, Alabama 



F. L. Mulford, U. S. Bureau of Plant Industry 



W. L. Bray, Syracuse University 



W. H. Osgood, Field Museum, Chicago 



E. A. Goldman, U. S. Biological Survey 



I. H. Blake, University of Maine 



Samuel Eddy, James Millikin University 



The associate editors did very much to improve the general character of 

 the work, but credit should be especially given Dr. E. Lucy Braun who read 

 the entire manuscript on states and provinces, making important general 

 criticisms. She added greatly to the plant material and verified the 

 scientific names. Dr. L. R. Dice made a similar careful study of the 

 manuscript on states and provinces and contributed materially to the 

 accounts of mammals. 



Several questionnaires regarding the nomenclature to be used for the 

 various communities and concerning the mapping of natural regions were 

 sent out. The names of the contributors of these subjects are in connec- 

 tion with the lists of natural regions and maps of them. 



The taxonomic nomenclature for plants in the states and provinces 

 is mainly according to Sudworth's Check List for trees, and for other 



