ACKNOWLEDGMENT 
Since the initial appearance of this work in preliminary mimeo- 
graphed form in 1936. a great many people have contributed original 
information and suggestions without which the present publication 
would be much less complete. To all of these people, the author 
wishes to express his sincere thanks. 
He is particularly indebted to Ernest G. Holt for his advice, sug- 
gestions, and criticism, as well as his very considerable assistance dur- 
ing the preparation of the manuscript ; to T. H. Kearney, for permis- 
sion to use his manuscript on the flora of Arizona ; to Y. L. Cory and 
H. B. Parks for the use of their manuscript catalog of the Texas 
flora, and Mr. Parks' manuscript on the useful XDroperties of Texas 
plants; to F. L. Mulforcl for the plant-growth region map, together 
with his chapter on its development; to C. W. Thornthwaite for the 
map of the climatic regions; to Clarence Cottam and his assistants, 
Phoebe Knappen, F. M. Uliler, Neil Hotchkiss, and A. L. Nelson, 
for their very great help in making available considerable data from 
the Section of Food Habits Eesearch of the Bureau of Biological 
Survey; to E. P. Killip for advice on the taxonomic problems: to 
E. L. Cranclali for his help with some of the photographs and to C. E. 
Ball, who assisted materially in the ^preparation of the section on 
Saliw. 
Suggestions and criticisms concerning the botanical material have 
been offered by E. J. Alexander, M. L. Fernald, E. J. Palmer, H. M. 
Eaup, H. A. Gleason, W. H. Camp, H. E. McMimi, F. J. Crider, 
C. Y. Morton, M. Yan Eensselaer, E. H. Graham, Mildred Mathias, 
H. L. Shantz. E, Y. Komarek, Hilda Cmmiff, Fred Gibson, and his 
assistant, J. YTiitehead, H. S. Yates. M. G. Netting, P. B. Sears, 
PI. L. Whitaker, C. F. Swingle, and Eussell Albright. 
Suggestions and criticisms concerning the wildlife material were 
received from Y^. L. McAtee, H. L. Stoddard. Aldo Leopold, D. M. 
Gorsuch, F. N. Hamerstrom, Jr., C. B. Terrell, E. T. King, Gardiner 
Bump, E. O. Stevens, A. M. Pearson, Logan Bennett, P. D. Dalke, 
Y. E. Davison, N. W. Hosley, ^Y. E. C. Todd, E. E. Yeatter, and 
H. D. Eulil. 
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