RESEARCH METHODS IN ECOLOGY BY FREDERIC EDWARD CLEMENTS, PH.D. ASSOCIATE PROFESSOR OF PLANT PHYSIOLOGY IN THE UNIVERSITY OF NEBRASKA _ILLUSTRATED_ LINCOLN, NEBRASKA THE UNIVERSITY PUBLISHING COMPANY 1905 COPYRIGHT, 1905 BY FREDERIC E. CLEMENTS AND IRVING S. CUTTER All rights reserved =Press of Jacob North & Company= LINCOLN, NEBRASKA 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 treatment 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 nomenclature 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 Professor 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 criticising the manuscript. Professor Goodwin D. Swezey, Professor of Astronomy 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, Director 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 students in experimental ecology, the author is indebted for many experiments which have been used in the discussion of adjustment and adaptation.