PREFACE 



The present volume is intended as a handbook for investigators and for 

 advanced students of ecology, and not as a text-book of the subject. An 

 elementary text-book covering the same field, but adapted to the needs of 

 undergraduate students, is in preparation. The handbook is essentially an 

 account of the methods used by the author in his studies of the last eight 

 years, during which a serious attempt has been made to discover and to 

 correlate the fundamental points of view in the vast field of vegetation. 

 No endeavor is made to treat any portion of the subject exhaustively, since 

 a discussion of general methods and general principles is of much greater 

 value in the present condition of ecology. The somewhat unequal treat- 

 ment given the different subjects is due to the fact that it has been found 

 possible to develop some of these more rapidly than others. Finally, it must 

 be constantly kept in mind that ecology is still in a very plastic condition, 

 and in consequence, methods, fundamental principles, and matters of nomen- 

 clature and terminology must be approached without prejudice in order that 

 the best possible development of this field may be attained. 



Grateful acknowledgment for criticisms and suggestions is made to Pro- 

 fessor Doctor Charles E. Bessey and Professor Doctor Roscoe Pound, who 

 have read the text. The author is under especial obligations to Doctor Edith 

 S. Clements for the drawings of leaf types, as well as for reading and crit- 

 icising the manuscript. Professor Goodwin D. Swezey, Professor of As- 

 tronomy in the University of Nebraska, has kindly furnished much material 

 for the determination of the sun's altitude, and consequent light intensities, 

 and has read the section devoted to light. Mr. George A. Loveland, Di- 

 rector of the Nebraska Section of the U. S. Weather Bureau, has contributed 

 many helpful suggestions to the discussion of meteorological instruments. 

 To Nella Schlesinger, Alice Venters, and George L. Fawcett, advanced stu- 

 dents in experimental ecology, the author is indebted for many experiments 

 which have been used in the discussion of adjustment and adaptation. 



Acknowledgment is also made to the following for various cuts : Henry 

 J. Green, Brooklyn, New York ; Julien P. Friez, Baltimore, Maryland ; C. H. 

 Stoelting Co., Chicago, Illinois; Draper Manufacturing Co., New York city; 

 Gundlach-Manhattan Optical Co., Rochester, New York; Rochester Optical 

 Co., Rochester, New York; Bausch and Lomb Optical Co., Rochester, New 

 York. 



FREDERIC EDWARD CLEMENTS. 

 The University of Nebraska, 

 May, 1905. 



