ACKNOWLEDGMENTS 



The author is deeply indebted to his associates at The Ohio 

 State University. Professor H. C, Sampson has had direct 

 charge of this general course since it was first given and has 

 conducted various experiments in teaching methods that have 

 greatly improved the efficiency of the course. He has read and 

 criticized the various revisions of the manuscript, has suggested 

 numerous changes in the text, and has contributed much both 

 to the form and substance of the book. Professor A. E. Waller, 

 Professor W. G. Stover, Dr. L. H. Tiffany, Dr. E. L. Stover, and 

 Dr. J. D. Sayre have read a part or all of the manuscript and its 

 revision. Without their cooperation and constructive ideas 

 neither the course nor the book would have had its present form. 



Professor H. N. Whitford, and Professor G. E. Nichols of Yale 

 University and Professor W. S. Cooper of the University of 

 Minnesota, made helpful suggestions regarding the chapters on 

 plant distribution. Dr. Cooper also generously supplied a num- 

 ber of photographs. The author's thanks are also due to various 

 men in the United States Department of Agriculture who have 

 furnished photographs of plants used in their investigations. 

 These are credited below the illustrations in the book. 



