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. 
